TOWARDS TASK TRANSPARENCY IN ALTERNATIVE COMPUTER ACCESS: SELECTION OF TEXT THROUGH SWITCH-BASED SCANNJNG
G. Fraser Shein
A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Mechanical and Industrial Engineering University of Toronto
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ABSTRACT
Current access technology for people with disabilities is based on a concept called transparency. Developen have generally interpreted this by building access systems that emulate the keyboard and mouse. In contrast, this thesis proposes and studies a refinement to transparent access. called task transparency. This approach has much potential impact on scanning access within a GUI. Here, scaming is applied to the underlying tasks, rather than emulating the input devices. The goal is to denve new knowledge and understanding of the interactions that anse with a number of strategies that apply switch-based scanning to text selection in a task transparent fashion.
In the case of selecting text. it was demonstrated that directness to the task could be achieved with minimal effort by applying scanning within the text area itself. The concepts are readily extended across other GUI objects including menus, buttons, and window controls. These objects can be incorporated within the access system such that they are directly engaged in the scaming. Through such strategies, usen can significantly reduce their efforts and in doing so achieve greater overall productivity, and accompl ish tasks that are otherwise strenuous.
Text scanning was implemented using repeating keys injected by an on-screen keyboard such that the user perceived scaming in the text area. Two test applications were developed and used to evaluate a number of proposed text scanning strategies. In addition, predictive performance models were derived to predict performance measures under error-fiee conditions. Initial design guidelines for scaming in a task transparent fashion were also formulated.
An access system developer could extend the concepts in new ways with scanning and other access methods. Future areas of research are identified that may improve overall productivity. Through this work 1 have conuibuted new knowledge towards improving scanning access and 1 have demonstrated the feasibility of task transparency by which further gains are possible. Acknowledgments
1 wish to acknowledge my advisor, Dr. Mark Chignell. who provided me with guidance and expertise in the developrnent of this thesis. I also acknowledge Dr. Mickry Milner and Dr. Steven Naumam of the Bloorview MacMillan Centre who guided me and provided ongoing support over many years at the Bloorview MacMillan Centre. Through their efforts 1 have bern able to hone my research skills and develop an ongoing programme of research related to cornputer systems for people with physical disabilities. 1 would also like to thank Dr. Paul Milgram for his insightful review and criticism that has helped me to bctter present my idsas.
1 extend much thanks to my research team, the Microcornputer Applications Programme. at the Bloorview MacMillan Centre who worked rnany long hours in developing the software solutions described here. In particular. 1 am grateful to Mr. Gil Hamann who assumed additional responsibilities during the final stages of this work and who provided in-depth rditorial and scientific review. Dr. Debra Fels provided encouragement and scientific review. Mr. Reinhard Schuller provided statistical and experimental protocol expertise as well as editorial revirw. 1 thank al1 of the staff at the Bloorview iMacMillan Centre who volunteered their time and cooperation as subjects within my sxperiments.
The National Health Training Programme of the National Health Research and Development Programme, Health Canada supported my initial research. The Bloorview MacMillan Centre provided resources and space. IBM Canada Ltd. kindly donated computer equipment. The final phase of my research was supported through the Ontario Rehabilitation Technoiogy Consortium supponed by the Ontario Ministry of Health.
Most of all, 1 extend rny appreciation to my partner. Patricia Stoddart, who persevered over many years and provided the constant encouragement and love required to complete this work. Table of Contents
1 Introduction ...... 1 i -1 Problem Statement and Motivation For This Thesis ...... 1 1.2 Research Goal and Objectives ...... 6 1.2.1 Goa1 ...... 6 1.7.2 Specitic Objectives ...... 6 1 -3 Scope ...... 7 1 -4 Road Map for this Thesis ...... 8
2 Literature Review ...... 1 O 2.1 Introduction ...... *... IO 2.2 Rrview of GUI Access by Users with Physical Disabilities ...... 11 2.3 Rrview of Indirect Scanning Access ...... II 2.4 Review of Models of Access ...... 2 1 2.4.1 Rehabilitation Engineering Models ...... 2 1 2.3.2 HCI Model of interaction ...... 27 2.5 Review of Transparent Accrss Approaches ...... 29 7-51 -4ltemate Kryboard and Pointing Devices ...... 29 2.5.2 Extemal Keyboard Emulating interfaces (KEI) and General Input Device Emulating Interfaces (GIDEI): Standard Ports ...... 32 2.5.3 Extemal KEI and GIDEI: Sena1 Input ...... 31 2.5.4 IntemalKEIandGIDEI ...... 35 2-53 Software KEI and GIDE1 ...... 36 2.6 Review of Mouse Emulators ...... 3 8 2.6.1 Keypad Mouse Ernulation ...... 38 2.6.2 Switch-Based Mouse Emulation ...... 40 2 .6.3 Non-Transparent Cornmand-Based Pointer ...... 40 2.6.4 Non-Transparent Scanning Screen Pointer ...... 41 2.6.5 Transparent Scanning Screen Pointer ...... 43 2.6.6 Scanning Screen Pointer Enhancements ...... 46 2.7 Review of Text Selection Methods ...... 47 2.8 Summary ...... 49
Task Transparency: A New Design Approach ...... 51 3 .L Introduction ...... 51 3.2 Interpretation of the Literature...... 51 3 -3 Task Transparency and Scanning ...... 55 3.4 Applying Task Transparency to Text Selechon ...... 58 3.4.1 Text Selection Task ...... 58 3.4.2 Keyboard Channel as Information Carrier ...... 60 3 .4.3 On-Screen Keyboard...... 61 3.4.4 Text Selection Scanning Strategies ...... 63 3.5 Overdrive Scanning ...... 70 3.6 Lmpact of Subject Factors on Text Scanning Strategies...... 73 3.7 Summaiy ...... 74
Development of Evaluation Tools ...... 76 4.1 Introduction ...... 76 3.2 Prediction of Error-Free User Performance ...... 77 4.2.1 On-Screen Keyboard Key Selections ...... 77 4.2.2 Select Switch Activations ...... 78 4.2.3 Time ...... 80 . . 4.3 Text Selecrion Test Application...... 83 1.4 Overdrive Test System ...... 86 4.5 Summary ...... 87 5 Evatuation of Text Selection Strategies ...... 88 5.1 Introduction...... 88 5.2 Prediction Methodology ...... 88 5 -3 Expenmental Methodology ...... 90 5.3.1 Goal ...... 90 5.3.2 Pilot Experiment ...... 90 5.3.3 Expenmental Design ...... 91 5.3 -4 Physical Arrangement ...... 92 5.3.5 Subjects ...... 93 5.3 -6 Data Analysis...... 93 5.4 Results ...... 94 5.1.1 On-Screen Key Selections...... 94 5.4.2 Select Switch Activations ...... 97 5.4.3 Cancef Switch Activations ...... 98 5.4.4 Task Time ...... 99 5.4.5 Potential Time improvements Through Keyboard Re-Layout ...... 101 5 .4.6 Errors ...... -103 5.4.7 Cornparison of Scanning Straregies vs . Standard Strategy ...... 106 5-5 Discussion ...... 108 5 .5 . 1 PlanninglMovement Strategies...... 110 5.5.2 Attention ...... 111 5.5.3 On-Screen Key Usage ...... 112 5.5.4 SwitchUsage ...... 113 5 S.5 Task Time ...... 115 5 -5-6 Errors ...... 117 5 .5 .7 Directness ...... 118 5.6 Summary ...... 119 Overdrive Scanning Evaluation...... 122 Introduction ...... 122 Methodology ...... 123 6.2.1 Goal ...... 123 6.2.2 Experimental Design ...... -123 6.2.3 Subjects ...... 125 Results ...... 125 6.3.1 Use of Overdrive ...... 125 6.3.2 Time Savings ...... 128 6.3.3 Errors ...... 131 6.3 .1 Subject Reports ...... 132 Discussion ...... 132 Surnmary ...... -137
7 Task Transparent Scanning Design Guidelines ...... 138 7.1 Introduction ...... 138 7.1 First Steps ...... 138 7.3 Guidelines ...... 139 Scanning Strategy ...... 139 hplementing Task Scanning ...... 140 On-screen keyboard ...... 141 Scan Interval ...... -142 Time Delays ...... 142 Canceling ...... 142 Emor Correction ...... 143 Feedback ...... -143 Starting/Stopping Scanning...... -144
vii 8 Conclusions ...... m...... m...... œ...... œ...... 144 8 .I Evaluation Conclusions ...... 144 8.2 Suggested Extensions to other GUI Tasks ...... 145 8.3 Insights Gained From This Research ...... 146 8.4 Suggested Future Research and Development ...... 147 8.5 Contributions...... 150 8.6 Final Words ...... 154
9 References ...... ~..gI..Img...ggg...~œa.m.m.Im.m..mg.gg...... m....155 List of Tables
Table 2-1 : Ideal selection set with respect to scanning dimension (Kulikowski, 1985)...... 20 Table 5-1: Average predicted and observed movement keys selected for each scanning strategy (* 95% confidence interval) per trial...... 95 Table 5-2: Average number of different sequences of key selections (*95% confidence interval) used to reach the beginning and end points...... 97 Table 5-3: Average number of predicted and observed select switch activations (* 95% confidence interval) to complete the experimental tasks per scanning strategy and session group...... 97 Table 5-4: Average time (seconds) (i 95% confidence interval) to cornplete the experimental tasks per scanning strategy and session group...... 99 Table 5-5: Count of instances in which the subject undershot the target with Strategies 3 and 4...... IO5 Table 56:Count of instances in which the subject overshot the target with Strategies 3 and 4...... 105 Table 5-7: Pros and cons of each of the scanning strategies...... 109 Table 6-1 : Usage zones of overdrive...... 126 Table 6-2: Total selection errors for both Methods, for the baseline and for the three overdrive scan intervals (0.33, 0.22 and O. 1 1 sec.)...... 130 Table 6-3: Number of subjects who preferred specific overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.) with both methods...... 13 2 List of Figures
Figure 2-1: Element scanning. Above. the black square indicates the current highlighted item while the gray squares indicates the previous highlights ...... 17 Figure 2-2: Row/column scanning ...... 17 Figure 2-3: Block/quadrant scanning...... 18 Figure 24: Row/column array indicating number of scan steps to select particular elements .... 19 Figure 2-5: Array of letters arranged according to Frequency-of-use ...... 20 Figure 2-6: Mode1 of an ideal altemate access system ...... 22 Figure 2-7: Multi-modal input mode1 ...... 24 Figure 2-8: Univenal Access System ...... 24 Figure 2-9: Transparent solution to interaction between a user and application through an intennediary alternative access user interface which may be tailored to the user ...... 25 Figure 2-10: Ideal interaction between a user and application through a single user interface which may be tailored to the user ...... 26 Figure 2-1 1: Direct approach of accessing the functionality of a computer system ...... 26 Figure 2-12: Overview of vimial protocol mode1 for computer-human interaction ...... 27 Figure 2-13: Transparent access through altemate keyboards and pointing devices . A kryboard may also ernulate mouse action...... 29 Figure 2-14: Transparent access through an extemal keyboard and mouse emulating device.... 33 Figure 2-15: Transparent access through an extemal keyboard and mouse emulating device that outputs standard GIDEI codes via serial link which are translated by a KEI, GIDE1 or SenalKeys...... 34 Figure 2-16: Transparent access through an intemal firmware/software keyboard and mouse emulating device that directly injects keyboard and mouse actions ...... 35 Figure 2-17: Transparent access through keyboard and mouse emulating software that directly injects keyboard and mouse operating system messages ...... 37 Figure 2-18: WiViK 2 on-screen keyboard...... 38 Figure 2-19: MouseKeys on the numeric keypad emulates a pointing device...... 39 Figure 2-20: Advanced-level Logo front-end on-screen keyboard displaying Blissymbol comrnands and back-end screen displaying Logo application ...... 41 Figure 2-21: Typical PIC-MAN screen layout with a simple drawing...... 42 Figure 2-22: Scanning screen pointer with horizontal and vertical movements...... 43 Figure 2-23: Scanning screen pointer with movement along user-selected heading ...... 44 Figure 2-24: Scanning screen pointer with rotating arcs highlighting in WiViK ...... 45 Figure 3-1: Task of moving screen pointer fiom point (x,, y,) to (x,, y, ) ...... 54 Figure 3-2:Task of moving screen pointer From point (x., y, ) to (x,, y, ) ...... 54 Figure 3-3: WiViK on-screen board text entry page with link to text movernent keys page ...... 61 Figure 3-4: Common WiViK on-screen keyboard layout for al1 scaming strategies ...... 62 Figure 3-5: Strategy 1 : Standard keystrokes to move the text cursor ...... 64 Figure 3-6: Strategy 2: Scanning text keys to move the text cursor ...... 65 Figure 3-7: Strategy 3: Sequential scaming text keys to move the text cursor...... 67 Figure 3-8: Strategy 4: Scanning text to select the insertion point ...... 69 Figure 3-9: Scanning periods: wasted time (A); preparatory time (B); and selection scan intemal (C)...... 71 Figure 4-1: Predicted scanning steps per movement key in the on-screen...... 80 . . Figure 4-2: Experirnental test application ...... 84 Figure 4-3: Screen arrangement of test application and WiViK on-screen keyboard showing partial completion of a block selection...... 85 Figure 4-4: Screen image of test application for overdrive scaming...... 86 Figure 5-1 : Physical arrangement of computer monitor, switches and subject...... 92 Figure 5-2: Relative proportional distribution of key usage with respect to the total number of keys selected per scan strategy ...... 101 Figure 5-3: On-screen keyboard re-design for fiequency-of-use with Strategy 1...... 102 Figure 5-4: On-screen keyboard re-design for frequency-of-use with Strategy 2 ...... 102 Figure 5-5: On-screen keyboard re-design for fiequency-of-use for Scan Strategy 3 ...... 103 Figure 5-6: On-screen keyboard re-design for fiequency-of-use for Scan Strategy 4 ...... 103 Figure 5-7: Performance improvement in total keys with Strategies 2-4 over standard keystrokes strategy observed in the experirnent and predicted based on optimal error- fiee movements...... 106 Figure 5-8: Performance improvement in select switch activations with Strategies 2-4 over standard keystrokes strategy observed in the experiment and predicted based on optimal movements...... 107 Figure 5-9: Performance improvement in total time with Strategies 2-4 over standard keystrokes strategy observed in the expenment and predicted based on optimal error- fiee movements with and without optimal keyboard layouts...... 107 Figure 6-1: Usage of the overdrive with respect to distance of target items and overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.) for both methods ...... 125 Figure 6-2: Proportion of observations within the 'yes' zone in which overdrive scanning began dunng the first, second and third or greater item scanned for each overdrive interval...... 126 Figure 6-3: Proportion of observations within the 'yes' zone in which overdrive scanning ended during the first, second and third or greater item before the target for each overdrive interval...... 127 Figure 6-4: Relative time savings to select target items for both methods and for the three overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.)...... 129 Figure 6-5: Distribution of rrrors for each target item for both methods and for the three overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.)...... ~...... ~...... 130 Figure 6-6: Theoretical time savings to select words using overdrive scanning at the word level with respect to sequential group scaming of 5 lines and 15 words/line...... 134 Figure 6-7: Theoretical time savings to select words using overdrive scanning at the word level with respect to sequential group scanning of 5 lines, 3 word groupsnine; and 5 worddword group...... 135
xii List of Appendices
Appendix A WiViK Keyboard Definitions: Evaluation 1 ...... 168 Strategy 1 : Standard Keystrokes ...... 168 Strategy 2: Scaming Text Keys ...... 169 Strategy 3: Sequential Scanning Text Keys ...... 170 Strategy 4: Text Scanning ...... 172
Appendix B Trial Selection Block Patterns: Evaluation 1 ...... 174
Appendix C Predicted Movements and Times: Evaluation 1 ...... 183
Appendix D Subject Instructions: Evaluation 1 ...... 195 Common Task Instructions (AI1 Strategies) ...... 195 Strategy 1 : Standard Keystrokes ...... 196 Strategy 2: Scanning Text Keys ...... 197 Strategy 3 : Sequential Scanning Text Keys ...... 198 Sirategy 4: Text Scanning ...... 200 Subject Reports ...... 202
Appendix E Condensed Data: Evaluation 1 ...... 203
Appendix F Statistical Analyses: Evaluation 1 ...... 208 Dependent: Total WiViK Keys Used ...... 208 Dependent: Total WiViK Keys to Set Insertion Point ...... 209 Dependent: Select Switch Activations ...... 210 Dependent: Cancel Switch % Usage (ArcTangent Transformed) ...... 211 Dependent: Total Time ...... 212
... Xlll Dependent: Count of Overshooting Target ...... 2 13 Dependent: Count of Undershooting Target ...... 214
Appendix G Predicted Times With Keyboard Rearrangement ...... 21 8
Appendix H Su bject Instructions: Evaluation 2 ...... 219 Overdrive Scanning Method 1 ...... 219 Overdrive Scanning Method 2 ...... 221
Appendix I Condensed Data: Evaluation 2 ...... 223 Overdrive Method 1 Average Times ...... 223 Overdrive Method 2 Average Times ...... 224
Appendix J Review of Design Guidelines for Alternative Access ...... -225
Appendix K Suggested Extensions to Other GUI Tasks ...... 230 Menus ...... 230 Window View ...... 232 Window Size and Position ...... 234 Dialog Controls ...... 235
xiv 1 Introduction
1.1 Problem Statement and Motivation For This Thesis
Many people with congenital or acquired disabilities can benefit fiom technology. Microcornputers. in particular. have provided people with the opportunity to lead more independent and fullrr lives (Bowe. 1985). People with disabilitia cmuse computers for the same purposes as any able-bodird person in areas of vocation. education and Ieisure. In somr cases, there are distinct applications that augment people's abilities, such as allowing communication for those who are non-speaking, or for environmental control. The important point is that people with disabilitics have the same need to access the same computers and software as rveryone else (Vanderheiden. 1982). In some instances, the use of computers by people with disabilities is of geater importance since it rnay be the only means by which they may gain independence in our society (Bowe, 1985).
Innovations in technology have advanced to the level where even the most severely physically disabled person can operate a computer (Bowe. 1987: Brandenburg and Vanderheiden, 1987: Buxton, Scadden, Foulds. Shein, Rosen and Vanderheiden, 1986). A multitude of access systems (Closing The Gap Hardware and Sofnvare Resource Guide. 1996) exists that utilize whatever physical ability a person may have to controba computer.
The current state-of-the-art in access technology is based on the idea of 'transparency' proposed by Vanderheiden ( 1982). Transparency refers to "a technique rhat is invisible to an! standard sofware program - rhat is. modifications cannor be detecrerl & a- standutad sofh.r.are rvhe~ithis technique i; ~ised"(Vanderheiden, 1982, p. 146). The general interpretation of transparency is that an alremare access solution shouid rrnu/ate the input device(s1 of a computer. Le.. kevboard and monse. such rhat the target application ir irnaware that the input is not /rom the standard devicels) (Cook and Hussey, 1985). Users with disabilities should then be able to equally access standard computers. operating systems. and applications. Although Vanderheiden (Vanderheiden. 1996, persona1 communication) did not intend this view of transparent access that focuses on device functionality. it has nevenhrless become cornmonplace. It may more appropriately be termed derice iransparenq*.
When users have severe physical limitations. and cannot directly access any altemate or modified keyboard. an indirect rneans of access is usually indicated. An example of indirect access is switch-based scanning with an on-screen or virtual keyboard (Anson. 199 1 ). An on-scrern keyboard displays a representation of a keyboard on the computer screen and contains keys that inject ksystrokes transparently into the target application when selected. Scaming involves the successive highlighting of items displayed in this keyboard. The user selects desirrd items by activating a switch when that item is highlighted. It is considered indirect becauss a switch action does not directly correspond to a keystroke.
Similarly. when users are unable to use the standard rnouse or some alternative pointing device. an indirect scanning solution is ofien considered. This generally involves sornr form of scanning screen pointer. To control the direction of movement. the screen pointer rotates in a scanning fashion. or a specific direction is chosen by scanning the on-screen keyboard. Then the screen pointer scans across the screen along the chosen heading. (Sze Section 2.6.5 for a description of scaming mouse emulation.) The current style of scaming screen pointers is derived fiom a design implemented by this author in an application that provided scanning access within a drawing application (Shein and Milner, 1985). Emulating a pointing device is considered necessary because pointing is an integral component of current graphical user interfaces (GUIS). It is also a fundamental concept of transparency that al1 keyboard keys and mouse functions must be available within the access system.
Indirect access through scanning is labonous and demanding on the residual abilities of the user. Much research and development has been done to reduce scanning time and switch activations through on-screen keyboard arrangement and rate enhancement techniques ( see Section 2 -31. Less research has gone into studying scaming screen pointers. although commrrcial developers have designed a variety of styles and enhancements that reduce the effort in using scaming pointers.
Surprisingly. no developer has questioned the basic need for implementing a scaming screen pointer at all. 1 suggest, however, that a scanning screen pointer is not necessarily required and hnher suggest that the current viewpoint of transparency diverts attention away from other potential access approaches because it focuses on device functionality.
While device transparency provides full functional access it does not always ensure that the user's interaction is effective or productive. With respect to tsxt entry. keyboard emulation with both direct and scanning access is generally effective because the keyboard function corresponds to the primary user task of entering text. This is not the case. however. for rmulating mousç functions. Indirect mouse rmulation is twice removed from most user tasks -by the indirect switch actions. and by the indirect poiniing reference to the user task such as selecting an objrct or performing a command. The additional loss of directness detracts from the direct manipulation features of a GUI and reduces the effectiveness of interaction.
This loss of directness is apparent in the following ways. Foremost, a scanning screen pointer forces usrrs to cmulate manipulative actions with which they may have no real-life rxpenences. Whereas an able-bodied person might use a mouse with little conscious effort. controlling a scaming screen pointer becomes a significant task in itself. It involves making decisions and accurately selecting appropriate directions and distances without direct reference to the underlying content. The user must connect the pointer to the data beneath it through visual matching. In moving the screen pointer via scanning, the user requires spatial comprehension that is not linked to physical actions and is withoui kinesthetic feedback associated with a mouse. Repetitive movement and attention switching between the scanning screen pointer and the on- screen keyboard can also be a hstrating experience for the user who only wants to select one comrnand. Thus, while device transparency suggests a scaming screen pointer, it is preciseiy that pointing interface that is inappropriate for scanning users. The end result is that usen who employ scanning minimally use the sca~ingmouse function. Rathrr. such users generally have a computer configuration such that they oniy access a single application with a limited command set placed directly within the on-screen keyboard. The exception to this is a drawing application. where the task is to move the screen pointer. which then acts Iike a pend tip.
It is proposed that more effective approaches to access can be designed following a rask
rt-ansparent approach. Alternate access syrems sho~~Zdjôllo~r~a design rhat alloir-sthe riser- ro direct(\*access the t A task trunsparency approach maintains the original concept of transparency but focuses attention on what the user wants to accomplish by working at the application task level. rather than the operaiional tasks associated with standard input devices. The objects. operations. and tokens of information associated with the user tasks are incorporated into the alternate access system. The user can then directly engage these objects and perceive a feeling of directly engaging the desired task. For example. the user may control a text cursor that scans across the trxt. This particular rxample is expanded upon within this thesis. Task transparency holds forth promise of increasing directness in the interface. It should help designers to clarie what the access system is enabling the user to accomplish. It should also overcomr the need to emulate physical devices that usen cannot operate in the first place. If al1 GUI objects to be selected and manipulated within the interface are considered to be part of a greater selection set (Cook and Hussey, 1995), a task transparency approach suggests that scaming be applied across specific objects and involve those objects directly in desired tasks. For example. menus. icons, buttons could be scanned directly. Users could move between objects by highlighting them in succession. select them with switch activation, perform a discrete function upon them by then choosing a command through scanning, or have those objects move in a scanning fashion. Users should then be able to perform desired tasks through a consistent access method appropnate to their abilities. This also follows the original transparency concept that the application interface should remain unmodified. Although it is possible to transfer current scanning methods desiped for on-screen keyboards to non-keyboard objects. it cannot be assumed that this transfer is transparent because the user tasks may change. An on-screen keyboard arranges a known fixed set of items within a rnatrix arrangement where they are scamed in an orderly fashion. Here. scanning ultimately leads to the selection of a single objrct within the on-screen keyboard. These objects are not manipulated. On the other hand. rnost GUI objects and related tasks are dynamically changing and have potentially very large member sets. e.g., text, menus. and lists of files. Some of these items are also manipulated in some way. e.g.. moved or sized. in which case a simple selection is not practical. It is not known whether there should be unique design and operational characteristics associated with sca~ingsuch non-keyboard objects. Nor is it established what additional demands will be placcd on the user and what impact these will have on performance. I suggcst that an access system must allow the user to achieve the desired task while minimizing physical (switch activation) and cognitive (planning, decisions. attention) rffons. errors. and time. The degree to which the user maintains control over the scaming task is anothcr concern brcause scanning stratepies tend to reduce user demands through pre-programming user actions. ix.. rnacro commands. Thsse strategies have the undesired side effect of reducing user control. This is particularly relevant when scanning a large and dynamic selection set such as text. A geat deal of time might bc 'wasted' scanning across many items before reaching the desired item because it is difficult to predict the number of items within groups that might be scamed. An approach called overdrive scanning (Lee et al. 1985) (see Section 3.5) has been implementrd in a number of access systems as an approach to permit greater user control to reduce the scan interval to permit faster scanning. However. it has never been formally evaluated. Although not al1 users rnay be able to take advantage of overdrive scanning as it is now implemented, it is important nonetheless to understand i ts po tential impact with respect to sca~ingdynamic selection sets. It is not feasible to study task transparency in depth for al1 potential GUI objects and scanning methods within the context of a thesis. Therefore, this thesis focuses on deriving new knowledge related to applying task transparency with one instance of objects that represents an important set and one that is dynamic and contains many items -text. Selecting text for editing remains a major problem for individuals with severe physical disabiiity. It is an ever-changing task with a very large number of possible acts and cannot be easily predicted. To date. the most effective means of editing is simply to use the 1.2 Research Goal and Objectives 1.2.1 Goal This thesis proposes a refinement to the interpretation of transparent computer access for people with physical disabilities, called task transparency. The goal is to derive new knowledge and understanding of the interactions that anse with a numbrr of strategies that apply switch-based scanning to text selection in a task transparent fashion. The results should provide valuable insights regarding the design of access systems that enable users of indirect scanning access mrthods to achieve not just rqual access, but to achieve equal productivity. 1-2.2 Specific Objectives This research undertakes analytical and experimental evaluation of a number of prototype scanning strategies as well as overdrive scanning within a GUI. These strategies target the fundamental task of selecting text with an emphasis on reducing user demands. mors. and tims. This information is used to develop initial guidelines for task-based scanning access and to providr a foundation for the extension of the approach to other GUI tasks. The user population that is being addressed is those individuals who are constrained to accessing a computer by switch-based scanning methods. Specific objectives are: ( 1 ) to devise and prototype strategies that apply switch-based scaming within a text field to select text; (2) to develop the necessary methods and tools to evaluate the prototype strategies and overdrive scaming rnethods, both analytically and experimentally; (3) to svaluate the effectiveness and relative ments of each prototype strategy in tems of demands on the user and resulting user performance: and (4) to suggest design guidelines and scanning characteristics that consider the evaluativr information regarding user demands and performance. 1.3 Scope Considering the many permutations of scanning strategies that are possible, this thesis focuses strictly on strategies for controlling an automatic scaming highlight moving across an array of items. analogous to text. using one or two switches for the purpose of selecting blocks of text. This stratem is a common strategy employed clinically. Other scaming techniques such as inverse and directed scanning are not examined. Nor are particular user settings considered such as scan rate (excrpt as it penains to certain settings tested in one rxperiment) and delay times which are genenlly set to specific user abilities. The experiments employed able-bodied subjects out of practicality to ensure a sufficiently large pool of subjects with homogenrous physical skills in order to identiQ the salient features of each strategy. A full rationale is provided in Section 3.6 (Impact of Subject Factors on Text Scanning Stntegies). The issue of concem is not how a person might intenct with a switch, but rather the effectiveness of a particular strategy given a fixsd sca~ingkwitcharrangement. Although scanning mouse ernulation is discussed here. it is not evaluated. This research does not srek to prove or disprove any contention that the proposed task transparency is better than current methods of mouse emulation. Until such time as the underlying design considerations are fully understood, a cornpanson of specific systems will have little significance. Nor would such a comparison yiçld a conclusion that holds for al1 users. However, arguments that identify specific drawbacks to sca~ingmouse emulation are presented. The intention here is to derive sufficient design information to develop alternative solutions that enable access in an efficient and productive rnanner and that are within the abilities of people for whom direct mouse emulation is not possible. 1.4 Road Map for this Thesis Chapter 2 reviews the literature of relevant GUI issues of concem. scaming methods. models of access. transparent accrss solutions, approaches to accessing mouse functions through scaming, and approaches to text selection. Chapter 3 outlines the proposed task transparency mode1 building upon the concepts identi fied in Chapter 2. A nurnber of proposed strategies are described that apply this approach to the task of selecting text. A strategy for reducinç scaming time. called overdrive scanning. is also descri bed. Chapter 1 describes the development of the predictive and sxpenmental tools that were used to cvaluate the strategics proposed in the previous chapter. Chapter 5 describes and discussrs the evaluation of the proposrd text scanning strategies applied to a representative set of text selection tasks. Chapter 6 descnbes and discusses the evaluation of overdrive scanning as a potential method of reducing time spent scanning across many items. Chapter 7 suggests a set of guidelines as a staning point for applying task transparent scanning throughout GUIS. These guidelines reflect knowledge gained through the evaluations conducted in this thesis. Chapter 8 concludes this thesis by summarizing the evaluations. outlining the insights gained from this research. suggesting future research and development, and speciQing my contributions. Several appendices are included that supplrment the presentation of this resrarch. Appendir A contains the WiViK on-screen keyboard definition files for each proposed strategy studied in Evaluation 1. Appendix B contains the trial selection block patterns for Evaluation 1 as they appear in the test application. Appendix C contains predictive data for scanning strategies studied in Evaluation 1. Appendir D contains the subject instructions for Evaluation 1. Appendir E contains condensed data for Evaluation 1. Appendir F presents the statistical analyses of the rxperimental data for Evaluation 1. Appendix G contains predictive time data for scaming strategirs studied in Evaluation 1 using on-screen layouts based on frequency-of-use data. Appendir H provides the subject instmctions for Evaluation 2. Appendis 1 contains condensed data for Evaluation 2. Appendix J contains a review of cxisting guidelines relevant to altemate access systems. Appendix K suggests ways of extending task transparency for several major tasks involving GUI objects. 2 Literature Review 2.1 Introduction This chapter presents a background of relevant literanire on research and devrlopment in altemate access systems to provide an undentanding of past and current design sternming from the concept of transparency. The specific research described here builds upon thesr concepts. This chapter begins with a review of the relevant issues of accessing GUIS by usrn with disabilities to providr a basis for achieving access through alternatives that still take advantage of the powerfùl notion of direction manipulation. This is followed with a review of indirect scanning which is the access method studied in this thesis. This provides a context to understand user drmands and the difficulties that anse in accessing a Gnphical User Interface (GUI). Models of access systems that have been developed within the rehabilitation engineering field are reviewed to provide sumcient background to understand transparent design approaches. These models providr a framework within which to apply scanning fdlowing the proposed task transparency approach. An abstract model of human-computer interaction is brkfly reviewed to provide a mort general understanding of the translation processes betwern the user and the computer. When the altemate access system has a substantial user interface itself, such a model can faciiitate our understanding of the interactions between the user and the access system. Specific examples of transparent access systems are reviewed that demonstrate the various configurations that can be implemented to achieve access. This is followed by an in-depth review of specific ways in which the function of a mouse can be implemented with scanning access. It is important to understand these approaches as the stimulus for this thesis. Text selection methods are reviewed along with pnor research conducted by this author on sca~ingtext. This describes the task addressed by this thesis and provides a starting point for my work. 2.2 Review of GUI Access by Users with Physical Disabilities A graphical user interface (GUI) incorporates a style of interaction called direct manipulation. In addition to the standard input of alphanumenc characters through a keyboard, the user indicates objects (icons, trxt. menus. and graphical objects) depicted on the screen and directly manipulates them with a pointing device such as a mouse. Shneideman ( 1987) points out that the key feature of a GUI is the notion of direct manipulation where objects such as text, menus, and graphical elements are manipulated using a mousr or othrr pointing device in a fashion analogous to real-world manipulation. For example. moving a document from one file folder to another. The pointing device govems the movement of a cursor on the screcn which serves as the user's "electronic finger," a vimial extension of the body (Brownlow et al. 1989a). In the real world we depend upon eye-hand coordination 10 get the job donc. Uscrs can take thrir cxperiences in the real world and apply them on the computrr that has a GUI and readily perform tasks that rnay be arduous with a conventional command-based interface. Shneiderman ( 1987) suggests that interfaces in this style are casier to lçarn. more efficient to use. and less awkward than their predecessors. In a GUI. a pointer or cursor. often in the shape of an arrowhead. moves on the screcn with the movements of the pointing device. The user points to. selects (by pressing one or more buttons on the pointing device). and manipulates objects (text. menus, icons. and other graphical objects) that appear on the screen. Examples of common direct manipulation tasks within a GUI include: placing a marker at a screen location; choosing a menu command: setting or adjusting screen controls such as scroll bars; re-sizing a window; seiecting a single object; selecting a group of objects: moving an object: drawing a line; and performing an action with an object such as formatting a block of text. While a GUI holds forth promise for quick and easy manipulation of data, the physical manipulation requirements are a roadblock for scanning users. Nevertheless. Brownlow et al (1 989b) highlight the potential benefits of direct manipulation even for users with disabilities. The key to the benefits lies in the 'directness' of such computer interfaces and how such directness can facilitate interaction and control. The challenge for designing access to a GUI is to maintain such benefits while providing alternatives to the physical manipulations. Hutchins, Hollan. and Norman ( 1985) suggest that semantic and articulatory properties of an interface contribute to the perception of directness. Two semantic properties of particular relevance are the use of a metaphor and the brevity of actions. An interface based upon a metaphor with which the user is familiar and which is consistent with their way of approaching tasks can be said to be semantically direct because tasks on the computer will not be different from non-cornputer experiences. A page layout application. for example. may be semantically direct if it allows the user to view a page çraphicaliy. and place elements of text and graphics on the page by picking them up and dropping them (with a mouse). This is very close to the manner in which a graphic designer thinks and works. This same example. however. could illustrate a semantically indirect interface if the user had no page layout experience, no ability to pick up objects. or impaired spatial concepts. Semantic directness is only achitved when the user can approach and makr use of a computer on their tems. not the cornputer's. Carroll. Mack and Kellogg ( 1988) suggest that the desktop metaphor that is common today does not reduce complrxity. but makes interaction more familiar and thus easier to use. They also suggest metaphors do not and cannot perfectly map the real-world to the computer and any mismatchcs introduce new complexities. Browniow et al ( 1990) suggest that if a person does not have the real world cxperitnce of manipulation because of some fonn of disability then the rntire basis behind a direct manipulation style interface breaks down. Someone with a physical disability may be unable to manipulate objects in the real world, let alone on a computer. Therefore. a metaphor that is less linked to reality might be advantageous since the user may not bring misconceived notions to the interaction tasks at hand. Brevity is another property of semantic directness. Usen should be able to specify a task concisely with few intewening maneuvers so that their focus is on the task and not on the actions required performing the task. Brevity of actions is one of the most significant issue for people with disabilities, i.e.. much can be accomplished through a few actions ( Brownlow et al. 1989b). Text-based interfaces oficn require long strings of commands. but may allow direct specification of tasks through function keys and key-combinations. While this achieves brevity. it lacks another quality of directness -the intuitive aspect of interaction. For example. novice users must stop and look up commands associated with fùnction keys in a reference guide because the keys have no meaning by themselves. A GUI does not always guarantee brevity; many actions. especially in dnwing programs. require unwieldy manipulations involving the pointing device and the keyboard in which the user must mernorize key-mouse combinations. An interface that allows the selection of commands directly would assist users with disabilities most of al1 (Brownlow et al. l99Oa). Articulatory directness refers to the expression of actions. In panicular. mimesis is a key facet where the signs that speci@ computer tasks. e.g.. icons or visual representations of objrcts within a GUI. mimic the tasks themselves. This follo~vsGibson's ( 1977) idea of affordance where the function of the object is obvious from its appearance. Dragging icons representing files from one folder io another or into a trashcan imitates real-life activity. The visual representation of the trashcan implies its function. This may be compared to command-based interfaces whrre words are used to perforrn similar actions. but the words do not resemble actual rnovements. Articulatory directness provides users with the impression that they are directly acting out actions on computrr objects. Yet it is suggested that the mimetic attnbutes of direct manipulation pose the greatest difficulties for people with disabilities. The requirement of physical pointing that mimics the way that people manipulate documents on a desk, is precisely what someone with a physical impairment may not be able to handle. Pointing actions may be broken down into a series of discrete steps that cmbe more easily selected, but this skins around and significantly delays the user's intention to achieve some goal. Brownlow et a1 (1 990b) proposed that an interface designed around delegation (Le.. by command) rather than manipulation might allow a user to cany out tasks in a marner that they have experienced. 2.3 Review of Indirect Scanning Access Scanning involves the successive highligbting or presentation of items in some display fi-om which the user selects a desired item (or group) by activating a switch when the item is highlighted (Hams and Vanderheiden. 1980). Common technologies that incorporate scanning include on-screen keyboards and augmentative and alternative communication (AAC) devices. Since switches require only binary (odomcontrol. single or multiple discrete switches can tap the residual abilities of people with the most severe physical impairments. Swi tch-based scaming is typically used by a person having severe motor incoordination due to a disorder such as crrebnl palsy. paralysis due to high spinal cord injury, or severe muscle weakness at advanced stages of muscular dystrophy or Am yotrophic Lateral Sclerosis (AL S ). Voice input is genenlly not an option for these users. Lee and Thomas ( l990) descnbe four general techniques of scaming: 1. In automatic scanning. a cursor or highlight automatically moves across groups or items. The highlight pauses at each group/item for a pre-set time called a scat1 itttm*al. Momentarily activating a switch usually stops the highlight over a larger group of items and initiates scanning of smaller groups or individual items. If the switch is activated when an individual item is highlighted. that item is selected. Timing of the switch activation is critical. Rather than tnck the moving highlight, users are taught to focus on the target item and activate the switch whenever the target is highlighted. They continue with this until the target is selected and scaming begins from the top. 2. Rather than the system controlling the speed of presentation, the user is in control with step scanning, although more switch activations are required. Here, repeated momentary activation of a switch advances the highlight. The advantage of this approach is that there is less timing pressure on the user. Groups or items are selected whrn highlighted by activating an additional selection switch, or by dwelling (i.e., pausing without selecting any switch). 3. With inverse scanning the user advances the cunor or highlight manually by maintaining switch activation. While the switch is activated, the highlight pauses at each item for a scan interval. Timing the release of the switch within a scan interval is important. Sometimes. step and inverse scanning are combined. 4. Direcied scanning associates separate switches with directions of cursor movement. These switches are usrd in a step or inverse fashion. The switches are often housrd in a gated joystick, allowing users to 'direct' the highlight, as they would drive a powered wheelchair. Items are selected by activating a selection switch. or by dwelling for some penod. Vanderheiden ( 1985. p. 23) describes this scaming method as a hybrid between scaming and direct selection because '.the selection is based on the type of movement made as well as the point in time that the movement is made." Many variations of these methods exist that depend upon the number of switches employed and scanning pattern. Vanderheiden ( 1985) presented a unitied modeling technique demonstrating the interrelationships among ail selection-based techniques including direct selection. scanning and rncoding. He used variable-branch tree structures to descnbc the selection algorithms. Al1 of the above scaming methods can be identified with Vanderheiden's model. as can any variation or new selection technique. Researchers at Bloorview MacMillan Centre (formerly the Hugh MacMillan Rehabilitation Centre) have implemented the rssentials of this general model within a scanning on-screen keyboard access system ( WiViKR2 Scan). A large variety of switches are commercially available for individuals to use with these scanning methods (Ciosing The Gap Hardware and Software Resource Guide. 1996). These switches Vary in contact surface area, property sensed (pressure. change in orientation, motion, relative positioning of components, degree of change), shape, contour, texture, and feedback (auditory, tactile. visual. kinesthetic) (Shein and Lee, 1983; Shein, Lee. Pearson, Milner and Pames, 1985; Lee and Thomas 1990). Lee and Thomas (1990) descnbe the following user actions to operate switches that Vary with scanning method: 1. a timed momentary activation (i.e., activate at a cntical instant with automatic scanning); 2. a non-timed momentary activation (i.e.. activats at any time with step and directed scanning): 3. a continuous activation with timed retease (i.e., release time is critical with inverse and directed scaming when selection is by release); and 4. a continuous activation with a non-timed release (i.e.. release time is non-critical with inverse and directed scaming when there is a separate selection switch). With these discrete actions. variations in movement speed. direction. or positioning do not affect the outcome of activating a discrete switch. Endurance becomes a critical concern with these actions because of the large number of repetitive actions to accomplish most tasks. Excessive repetition of movements may lead to fatigue and strain injury (Cantor. 1995). One rhrough five switches are commonly used for scanning. Single switches are most frequrntly used for timcd activation in an automatic scanning system. typically a row/column array. Occasionally they are used for inverse scanning. In the latter case, the user selects an item by releasing the switch for a pre-set period of time. A second switch is ofirn used to augment single- switch scanning techniques. In automatic scanning. the second switch ofien provides an 'escape' or 'cancel' function, and in step or inverse scanning it acts as a selcction switch while the first switch is usrd to move the highlight. Threr switches are not very common, although they can provide somr additional control. For rxample. momentary activation or timed release of one switch may advance the cursor from lefi- to-right, while similar movements of a second switch may move the cursor from top-to-bottom. Releasing and reactivating one of these switches reverses the scanning direction. Momentary activation of a third switch signals selection. This approach has the advantage of enabling users to back up quickly if they accidentally scan past a desired item, instead of having to wait through another scanning pass. Five switches provide a high degree of discrete switch control for directed scanning. Momentary activation or timed release of four switches, such as a microswitch joystick, directs the cursor within a two-dimensional scaming array. A momentary activation of the fi Ah switch selects the item under the cursor. Associated with automatic, step and inverse scanning are particular patterns by which the scanning highlight moves across the matrix of keys. These patterns include clement. row/column. and block scanning. In an element scan. the cunor proceeds to highlight each item of a matrix in succession. usually From lefi-to-right and top-to-bottom (Figure 2-1). After a selection. the cursor generally retums to the fint item and repeats scaming. Element scanning is typically limited to less than 15 items (Vanderheiden and Lloyd. 1986). Figure 2-1: Element scanning. Above, the black square indicates the current highlighted item while the gray squares indicates the previous highlights. Row~columnscanning is a faster selection technique in which rows of items arnnged in a two- dimensionai matrix are scanned row-by-row from the top down (Figure 2-2). A selection made with the single switch stops the scanning at a panicular row which is subsequently scanned column-by-column until the desired item is reached and selected. As before. the cursor retums to the first row to repeat scanning afier a selection. Figure 2-2: Row/column scanning. A third approach. block scaming, is best used for large matrices. One variation of block scanning is quadrant sca~ing(Basacchi, 1982) which is used with a square rnatrix of items. The matrix is divided into quadrants. Staning fiom the top lefi-hand quadrant, each quadrant in the on-screen keyboard is highlighted in succession. When a 'select' switch is activated. the currently highlighted quadrant is selected and scaming is repeatrd within that quadrant until individual elements are scamed (Figure 2-3). This is a vrry efficient selection technique where one of 4" items can be selected with n switch activations. Figure 2-3:BlocWquadrant scanning. Treviranus ( 1994) descnbed additional variations of this block scanning involving successivrly expanding quadrants, halves. and diarnond facets. For large matrices of other dimensions, blocks of items of irregular sizes may br scanned in a similar fashion. However. these blocks must be pre-defined for scanning or a sprcial algorithm rnust be creared such as one based upon a model sugpested by Vandrrheiden ( 1985). A funher variation of block scanning entails arranging items on different pages or windows thar are then scanned. Appropriate presentation of the selection set is important to ensure effective and efficient interaction with the cornputer. Shein ( 1988a.b) suggested that there are two key issues in relation to the presentation that drive the design of scanning access: (a) locating the desired item within the set: and (b) getting to that item to select it. Physical characteristics of the items, such as size. font. boldness. colour, precision. letter and line spacing are important for ensunng that the desired item can be quickly located. The total number. arrangement and placement of items facilitate scaming to a desired item. Since scaming is inherently slow, techniques have been devised within the rehabilitation field to decrease delays between selections: andor decrease the number of selections necessary to fom a message. Delays between selections can be reduced through appropnate arrangement of items. Specifically, distances and the number of items scanned can be minimized based upon knowledge of the frequency of occurrence of single leners, letter diprams and trigrams. and word usage (Vanderheiden. 1985: Vanderheiden and Lloyd. 1986; Getschow. Rosen and Goodenough- Trepagnier. 1985). These Frequency-of-use arrangements are organized in relation to the scanning pattern. For example, consider row/column scanning with a single switch as the input device. Lrrten can be arranged according to their frequency-of-use starting from the upper lefi-hand corner and radiating doun and across the display fiom the most to the least frequent (Foulds. Balesta and Crochetiere. 1 975: Heckathome, and Leibowitz, 1985). Figure 2-4 illustrates the number of scan steps needed to select each item in a matrix using row/column scanning. For example. the 2nd item in the first row and the 1st item in the second row both require 3 scan steps ( 1 row and 2 items. and 2 rows and I item respectively). The time taken to scan to an item can then be calculated by multiplying the number of steps times the scan interval. Figure 2-4: Row/column array indicating number of scan steps to select particular elements. Figure 2-5 shows how the alphabet may be arranged with fi-equently used letters assigned to positions with lower number of switch activations or scan steps required. Figure 2-5: Array of letters arranged according to frequency-of-use. Such arrangements of items are dependent upon the dimension of the scaming (i-s..numbrr of successive sub-groups). For rxample, item scanning has a dimension of 1 while row-column scanning has a dimension of 2. Quadrant scaming of an 8x8 matrix has a dimension of 3 (cg.. 8x8 4x1 + 2x2). Funher groups or pages of items can generate additional dimensions. Added dimensions can ensure that the number of scan steps to reach any item is minimized. Kulikowski ( 1985) drscribed the ideal relationship (fewest average scanning steps) between scanning dimensions and the selection set size as show in Table 2-1. 1 Dimension 1 Selection Set Size Table 2-1 : ldeal selection set with respect to scanning dimension (Kulikowski, 1985). For example, when the selection set contains between 6 and 22 items. it is most efficient to arrange these items in a matrix and use row-column scanning. For example. 20 items might be arranged in a 3x5 matrix and scanned by rows and columns. Then. when the set increases between 22 and 85 items. it is more efficient to use row-group-item or quadrant scanning. For examplr. 64 items might be arranged in an 8x8 matnx and scamed by quadrants. It should be noted that these ideal dimensionkize relationships do not reflect natural language or other groupings of items in a selection set where the visual cue associated with the grouping is of greater importance in locating an item than the number of scan steps. 2.4 ReviewofModefsofAccess 2.4.1 Rehabilitation Engineering Models Vanderheiden ( 1 985) described a simple three-stage model of selection-based aupmentative and alternative communication (MC)techniques that parallels computer input. The first stage involves interpreting signals from the user through some input tnnsducer (cg.. switch). The second stage applies some selection algorithm to increase the number of available selections unless the user can directly select each item. Al1 scanning methods are applied at this stage. And the third stage. maps selections to messages that optimize output. Vanderheiden's model is usefbl and relevant for this discussion of cornputer access because it suggests the independence between different levels of interaction such that if the user has difficulty with one aspect then it can be replaced or augmented with another at that same level. Funher. very limited input can be used to access a large selrction set for improved production. These ideas form the basis for al1 alternative access. MacDougall et al ( l989a.b) outlined a more comprehensive model of alternative access (Figure 2-6) that is appropriate for both AAC devices and cornputers. * 1. lnput 2. Input 3. Input 4. Seledon 5. Input 6. Translation + -b Device -b Tramiaoon * Filter Technique * M-ng a Application Targe t USER ~pplication 1 1. Outpuf + t O. Output , 9. Merge . 8. Output 7. Translation F Device Translation FdW Mapping + from Applic. b Figure 2-6: Model of an ideal alternate access system In this model, the user physically controls an input device, whose signals are converted (usually by a device driver) through input translation into a standard format. Two basic input translators are generally incorporated in a cornputer: one for the keyboard, the other for a pointing device. In the case of a scaming system a translator must also be available for switch activations. Input filters enhance the input signal, reducing or eliminating undesired input signals. A selection technique uses the filtered input signals to pick items from a selection set (not shown). Selection sets can contain alphanumetic characters, words, phrases, and other data symbols as well as commands to the system; techniques include direct selection (as in typing or pointing) and vanous forms of switch-based scanning. To enhance user production, input mapping can be used where the selection set contains simplified labels that map ont0 more complex sequences of symbols and commands (e.g., macro definitions). These are then translated to the application through codes required by the target application. MacDougall et al (1988a) suggested that the input translation module is most practically implemented following an earlier suggestion by Vanderheiden (1 982) to transparently input equivalent codes as standard devices. Device independent primitives, such as in the Graphical Kernel System (GKS)(Enderle, Kansy & Pfaff, 1984; and Rosenthal et al, 1982) rnay also be used if the operating system is designed to understand such primitives. The application's information must be translated frorn the application so that output mapping can provide information in a sensory modaliry (visuai. auditory. or tactile). representation. and presentation format which the user can perceive and undentand. MacDougall et al ( 1988) and Fels ( 1994) suggest a series of modality-independent primitives as way to achieve this. Since a number of other processes also generate information. their feedback is merged with the application feedback for presentation consistency. This feedback passes through an output translator to derive signals that drive one or more outputs which ultimately presrnt information to the user. A separate process. an operation assistant. oversees the interaction of al1 other components. and allows the user to modify the parameters of the access system. Demasco, et a1 ( 199 1 ) drvrloped a sirnilar mode1 based on software object classes that could br cornbined to form a variety of AAC systems. Demasco ( 1989. persona1 communication) criticized the model by MacDougall et al because it did not explicitly support iterative interaction involving dynamically changing selection sets associated with word prediction before any input reaches the target application. The model that Demasco's team designed allowed such interaction (Demasco. et al. 199 1 ). Shein et al ( 1990) identified the single channel of input associated with scanning access systrms as a serious limitation. This limitation is being addressed by researchers who are developing models of access that account for multi-modal input (Cairns. Sman and Ricketts. 1 994: Roy. et al, 1993). Cairns. Sman and Ricketts proposed a model whereby several input devices could connect to a translator that convens combined input into keyboard and mouse events as show in Figure 2-7. As an example. they suggested that a user might use eye-gaze to point, and use speech recognition in place of bunon presses. n Keyboard Events 4 Joystick Multi- Modal Application EyeGaze 1 1 System 4 Switch Mouse Events Standard Alternate Input Devices lnput Devices Figure 2-7: Multi-modal input model (Cairns, Smart and Ricketts, 1994, p. 399). Although Cairns. Smart and Ricketts explicitly described their systrm as generating standard keyboard and mouse input. they also suggested that their translater generatr sets of efkcts such as button pushrs and slider movements. Thus. they were considenng the actual tasks being dons by the mouse. although not the underlying task that the user was trying to accomplish. Treviranus et al ( 1 99 1 ) described an al ternate view of multi-modal access where one input method was used with two selrction methods simultaneously. In her study. non-speaking users employed uttenncrs to control an on-screen keyboard. If the utterance was distinct. the user directly srlectrd a ksy. otherwise they sca~edto it. Selection was by an utterance. Scott ( 199 1 ) proposed a model of a 'Universal Access System' based on an extemal device. such as a portable computer. which maintained the user's accessible interface which in nirn communicared via infrared link to the host application system as shown in Figure 2-8. b Host Universal Access Link Accessor User Computer 4 I Universal Access Port & Host Driver Software Figure 2-8: Universal Access System (modified from Scott, 1991, p.65). This approach requires a 'Universal Access Port' and 'Host Driver Sofbare' on the host computer to translate keyboardimouse input and application events. In concept, Scott's model is similar to the model suggested by MacDougall et al and its design is similar to early alternative access systems (Crabtree. Korba. Nelson & Park. 1982: see Section 2.5.2) with the additional feature of receiving feedbac k from the application. While this approach maintains device transparency. the user is lrfi to contrnd with both their own access system's interface and the application's user interface. This is not a senous issue whrn the keyboard and mouse are replaced with altemate physical devices. However. problems can arise when the replacement involves indirect access. such as with scanning an on-scrern kryboard. As can be sern in Figure 2-9 the user must contend with feedback from two user in- terfaces which can be a source of confusion and error (Shein. 1987. MacDougall et al. 1988a.b). - Alternate - 4-- - Access - User . Application User Application I Interface I Figure 2-9: Transparent solution to interaction between a user and application through an intermediary alternative access user interface which rnay be tailored to the user. Two 'rxtrmal rnyths' (Rubenstrin and Henh, 1984) or conceptual models must be dealt with by the user in this transparent model. e-g., a direct manipulation style GUI and a discrete selection scanning on-screen keyboard. Ideally, blending the extemal myths as much as possible should minimize the differences between the two user interfaces. This has not happened. Afier the concept of transparency was put forward by Vanderheiden, attempts to modiQ an application's user interface have been frowned upon as being too costly and as a funher segregation of dis- abled from able-bodied users. Scott (1 99 1 ) claimed that even combining the altemate access system on the application computer system does not provide equal access because it does not ensure that the user can access any and al1 cornputers that they may encounter. However, this author pointed out that so much Mie and effort have been spent in ensuring solu- tions do not require any changes to the application's user interface that the issue of how best to support interaction for a paxticular user with unique abilities has been overlooked. 1 had proposed that an alternative access system should be another instance of a user interface blending the alternate access with the standard user interface (Figure 2-10) rather than acting as a bridge of keyboard and mouse signals. While the idea of separating the application from the user interface is shared with the philosophy associated with user interface management system (Tanner and Buton. 1985) and device independence. such as with GKS. this concept of replacing the user interface is not practiced within the field of rehabilitation engineering. 4 Alternate Access/ User - Application User Interface 1 Figure 2-10: Ideal interaction between a user and application through a single user interface which may be tailoreci to the user (Shein, 1987; MacOougall et, 1988a. p. 24). Adams and Abbon (199 1 ) descnbed a supporting arrangement of accessing the underlying fûnction of the computer rather than just keyboard and rnouse actions as shown in Figure 2-1 1. 1 Software User Key board Functionality lnterface and Mouse I I Alternate User Interface I t User Figure 2-1 1: Direct approach of accessing the functionality of a computer system (Adams and Abbott, 1991, p. 56) They suggested that the altemate access system provide input at three levels: by cmulating keyboard and mouse actions; by acting directly upon application user interface objec ts (e-g.. buttons. menus); and by acting directly upon underlying software functions (tg.. commands. opentions). In the case of sca~ingaccess. they proposed that the scanned elements could be GUI objects. Also. some underlying functions having some difficult or awkward GUI representation or keyboard access could be directly selected From an on-screen keyboard. 2.4.2 HCI Model of interaction Nirlsen (1986) proposed an abstract virtual protocol model for computer-human interaction shown in Figure 2-12 that is usehl to understand the human-orientcd translations rather than the devicç-oriented translations of the rehabilitation engineering access models. Human Corn puter Goal Level OI1C ..-..TV...... *..*-.. --...... Task--.-- ....Level -.- ---.---..-...... - ...... *...A...... -...A--. -- . ..- . -. . -. .- ....- ...... Semantic Level...... Invisible ...... *...-. ....*- ...... Syntax...... Level ...... Visible -...... Lexical Level .....------.-..--.--*-.-.--- ...... Physical Level .-.--.--- ...... Virtual communication +-. -----. .-- 7Physical Communication Realizer Analyser Figure 2-12: Overview of virtual protocol model for computer-human interaction (Nielsen, 1986, p. 302) Foley and VanDam ( 1982) and Buxton ( 1983) have suggested similar models. Typicai of these rnodels are layers of both invisible translations that go on in the user's mind in translating intrnt into realizable actions and visible portions of the interaction. in Nielsen's model, goals operationally describe what the user is trying to achieve with the computer. For example, the user may wish to edit a certain section of text. At rhis level. operation of the input device is not a concem. Tasks are concemed with applying the goals in terms of cornputer-related objects and operations. An example would be copying the last sentence in the first paragraph in the document being edited. The semanric layer deals with the hnctionality or meaning of the interaction. An exarnple is a command to copy a srlectrd sentence. Al1 of these layers in the model are said to be invisible to the user. although the user is aware of them. The sjntactic layer descnbes the rlrments of control and the specific order of events that the user follows. For rxample. the user rnay select the sentence then choose a copy command (noudverb syntax). This layer begins the visible part of the interaction because the user actively carries out actions. The lexical layer is concemed with detailed interactions at the information level in tems of units of "information-canying symbols of interaction." Examptes are screen coordinates and commands such as COPY. The alphnberic layer contains the primitive bits of information that have no direct meaning but can be combined and understood in system terms. Le., tokens in the lexical layer. The p/qsical layer deals with the actual physical movements that the user is prrforming with the input device to manipulate the information in the above layers to achieve the user goals. Buxton ( 1983. 1986) placed a strong emphasis upon the pragrnatics. or practical considerations. of physical interaction between the user and the systern. Certain1y, for persons wi th disabilit ies, this pragmatic component is one of the prime considerations in the design of an access system. Funher, Buxton suggests that this pragmatic component is not a distinct layer in a user interaction model but is linked to al1 visible levels. 2.5 Review of Transparent Access Approaches Vanderheiden ( 1982) fint described transparency in relation to text input. but as GUIS came into common usage in the late 1980s. transparency to mouse functions was assumed. Transparency has revolutionized access for people with disabilities and has becorne the accepted approach because it allows developers to create cost-effective solutions with wide applicability. This approach is in contrat to a non-transparent approach where an application is devrloped with altemate access as part of its inherent user interface. The various ways in which transparency cm be achieved is reviewed in the following subsections. 2.5.1 Alternate Keyboard and Pointing Devices At the device level. alternate keyboard or pointing devices can connecr to the standard input ports if they gennerate equivalent input signals to the standard devices as illustrated in Figure 2-13. There are many commercial keyboards and pointing devices designed for average computer users that meet this description. These Vary in physical dimension. sensitivity. and method of control. Examples of altemate keyboards include space-saving keyboards. rrgonomic split keyboards, and one-handed chordic keyboards. Common alternate pointing devices include trackballs. touchpads. touchscrerns. pens. and force joysticks such as the TrackPoint.' AI1 of these devices require direct accsss abilitiss by the user. Alternate Actions Standard Corn puter I 1 Actions 1 Figure 2-13: Transparent access through alternate keyboards and pointing devices. A keyboard may also emulate mouse action. International Business Machines Corporation. White Plains. NY Nelson. Park, Farley & Côte-Baldwin ( 198 1 ) descnbed how the necessary keyboard emulating hardware that outputs standard keycodes can be built into special keyboards for penons with disabilities. Kelso and Gunderson ( 1984) proposed a generic keyboard emulating interface (KEI) architecture that accounts for the differing electrical charactenstics of different computer keyboard ports. A number of devices designed specifically for users with disabilities are now available for both keyboardmouse input (e.g.. ~ntelli~e~s:,Magic Wand ~eyboard'.TASH King and Mini ~e~boards').These devices also incorporate keys that provide mouse emulation (sre Section 2.6.1 ) becausr using a separate pointing device is ofien quite difficult (Brownlow et al. 1990a). The main reason for this difficulty is that the region where a person has greatest control is ofien limited and positioning two input devices within this region is ofien not possible. Expanded keyboards rxtend the dimensions of the keyboard, the sizr of individual keys. and the spacing between keys. This may be nrcessary for someone who has poor targeting ability owing to a muscular disorder such as cerebral palsy. Miniature keyboards are suitable for people with a limited range of movement. such as those with muscular dystrophy. To operate a miniature keyboard. users hold a stylus in their hands. pointing to and selecting keys through wrist action alone. Frwer specialty pointing devices have been developed for people with disabilities brcause there is such a plethora of commercial devices available. In some cases. devices are modifird if the user has dificulty with some aspect of its operation. such as activating the burton or grasping the device (Brownlow et al, 1989a; Treviranus et al, 1990). A number of specialty devices have been developed that take advantage of headpointing that work in conjunction with both physical and on-screen keyboards (e.g.. ~ead~aster'; ~ead~ouse~. ~racker ). Suc h headpointing devices have : InteIlitooIs. Novato. CA ' In Touch Systems. Spring Valley. NY ' TASH. Inc.. Ajax. ON Prentke Romich Company. Wooster. OH " Origin Instruments, Grand Prairie. TX Madenta Communication Inc.. Edmonton, AB less appeal for able-bodied users although they could be used to eliminate the necd for users to take their hand away from the keyboard to point. In sorne cases, keyboards might use special input drivers for additional feanirrs or functionality to accommodate the unique abilities of the user. Such accommodations are intended to provide the user with the perception that their input is free of error and accurately reflects their intended input. Researchers at the Trace Research and Development Center (Madison. W 1) have developed a number of such accommodations which are incorporated within current operating systems such as DOS'. OS@, Windows 95" and Macintosh OS" (Lee & Vanderheiden. 1988; Novak. 1992: Novak. Schauer, Vanderheiden & Borden, 1994): StickyKeys allows an individual to sequentially select a modifier key and anothrr key rather than having to press them simultaneously, e.g., Pointing devices often have certain filters incorporated in their drivers (Hansen and Wanner. 1993). For example. a pointing devicr may be limited in the horizontal or vertical planes. or restricted to orthogonal movemrnts. An extension of this is to limit movement to discrete steps or blocks. Filters may also be used to ampli@ small input, or to lessen large input. If users empioy a pointing device, and their resolution of control is poor, then the scaling can be such that a large movement with the device corresponds to a small displacement of the screen pointer (Brownlow et al, 1989a: Shein et al, l992a). In some cases it may be appropriate to exercise ' International Business Machines Corporation. White Plains. NY International Business Machines Corporation. White Plains. NY :" Microsoft Corporation. Redmond. WA " Apple Computer Inc.. Cupertino. C.4 proponional scaling based upon speed or timing of input. Le.. the distance that the screen pointer moves may multiply as the speed of the pointing device increases in a particular direction. There are other accommodations that expand selections through a mapping process as suggested in the above models of Vanderheiden and MacDougall et al. Three primary methods of input mapping are commonly used: one-to-one rnapping: characters. words. phrases or sentences are entered as displayed: rnacro or abbreviation-expansion mapping: one or a few letters or symbols are displayed and a complrte message or command string is entered whrn selected (Roa & Riley. 198 1 : Vanderheiden, 1983; Beukelman & Yorkston. 1984; Stum & Demasco. 1992): and predictive mapping: a list of predictions of what the user intends to select is displayed following one or a few initial selections: a selrction enters the predicted word (Swiffen. Alm and Newell. 1987: Darragh. Witten and James. 1 990). 2.5.2 External Keyboard Emulating Interfaces (KEI)and General Input Device Emulating Interfaces (GIDEI): Standard Ports A variation of the previous approach is to have an extemal device. such as an AAC device or second cornputer-based altemate access system emulate the keyboard andior mouse (Figure 2-14). Such a drvice could physically connect directly to standard input ports. The advantage of siich a system is that any selection method can be used and the acccss system is independent of any computer manufacturer and operating system. Early devices such as the MOD Keyboard (Crabtree. Korba. Nelson & Park, 1982; Lee, Shein, Pames and Milner. 1985) used a second inexpensive computer to 'front-end' a target computer to provide keyboard emulation through a varkty of switch-based selection methods. This computer included additional hardware to allow the physical comection to standard pons (Korba, Nelson & Park. 1984). Doubler, Strysik and Heckathome ( 198 1) built a similar device that was microprocessor-based. These early devices followed the Keyboard Emulating Interface (KEI) concept proposed by Vanderheiden (1 980). nti/GlDEl Mouse Keyboards Actions Figure 2-14: Transparent access through an external keyboard and mouse emulating device. The KEI concept was replaced by the Genenl Input Devicr Emulating Interface (GIDEI) concept in the late 1980s to account for mouse emulation required with GUIS. Only a few such drvices are commercially available today that follow this concept (DARCI TOO':. LUCY Alternative ~e~board",~ini~orse". NOPS Keyboard Simulator"). Separate mouse emulating devices have also been developed that similarly translate switch actions into mouse input (e.g., ~ouseEmulator'".~ouse~over"). Marsden and McGillis ( 199 1 ) described an extension to this concept for the Macintosh cornputer where its standard pon. the Apple Desktop Bus (ADB)"permits more than kryboard and mouse input. Thus, transparent accessibility of the underlying functionality of an oprrating systrm as suggested by their colleagues Adams and Abbott (l99 1 ) could be achieved (see Figure 2- 1 1 ). Marsden and Lewis ( 1 995) elaborated upon this schrmr by using underlying operating systrm messages to achievr access to hnctions. Thry also proposed a standard protocol for communication between an access system and the operating system architecture. :' WestTesr Engineering corporation. Bountiful. UT '' Words+. Inc.. Palmdale. CA ' Bloorview MacMillan Centre. Toronto. ON :'MCAP GmbH. Pforzham. Gerrnany :" Adaptivation. Inc.. .Ames. IA TASH. Inc.. Ajax. ON :' AppIe Computer Inc.. Cupenino. CA 2.5.3 External KEI and GIDEI: Serial Input Rather than requiring an external device. such as an AAC device. to gsnsrate keyboard and mouse signais for al1 computers, researchers at the Trace Center suggested that such devices generate a standard set of GIDEI codes (Schauer, 1 990: Standards Project Manager. Trace Center. 1994). Codes consist of ASCII chancters or The serial link connects to either (a)an intermediary keyboard/mouse smulator such as the T- TAM"'(Kelso et al. 1990) which in mm connects to the standard keyboard and mouse ports: or (b) the serial port whereupon it would be interpreted through software called SeriaIKeys which injects appropriate key and mouse messages into the operating system (Novak & Leubben. 1995) (Figure 2-15). It is another standard access feature associated with StickyKeys and others described in Section 2.5.1. Switches Keyboard GlDEl KEI, Actions Access GlDEl Standard System or Computer )I -1 -1 KEI/ SerialKeys Mouse Keyboards GIDE1 Actions u Figure 2-15: Transparent access through an external keyboard and mouse emulating device that outputs standard GIDE1 codes via serial link which are translated by a KEI, GIDE1 or SerialKeys. Standard GIDEI codes enable a device to generate al1 possible ASCII codes and mouse actions even if the device does not have al1 keyboard and mouse actions pre-programmed. An advantage of GIDEI code with respect to mouse emulation is that it converts al1 mouse actions, including movements and button clicks, into discrete selections. This frees the device to implement mouse * Prentke Romich Company. Wooster. OH actions in non-conventional ways. For example, the Libentor allows the user to jump to a region of the scrern before moving to the target. Actual distances of cursor movrments are definable. thereby ailowing gross. or fine. movements. 2.5.4 Interna1 KEI and GIDE1 The Adaptive Firmware Card (AFC) (Schwejda and McDonald. 1982: Schwejda and Vanderheiden. 1982) was a KEI that consisted of both a finnware card that fit inside of the Apple II' computer and software for a variety of selection methods. The 4FC supponed a single-line pop-up on-scrcen keyboard along the bottom of the screen. Morse code. remote keyboard connection. and ssrial and parallel ASCII keyboard input. Selections were sent directly to the ktyboard buffer of the cornputer as if they came fiom the standard kqboard. This concept is shown in Figure 2-16. Standard r-l cornputer Switches Alternate Keyboards Actions Figure 2-1 6: Transparent access through an interna1 firmware/software keyboard and rnouse emulating device that directly injects keyboard and mouse actions. Schwejda and McDonald (1982) acknowledged that the interrupt nature of this type of technology was a disadvantage. When an input device was activated. the target application stopped, and the AFC software display routines were called. The application then continued afier a selection was made or afier a penod of no selection. :"Apple Computer Inc.. Cupcnino. CA More recently, the PCMCIA or PC Card has been used as a GIDEI (Luebben and Novak, 1995: Morse Code Darci card2!).This injects key and mouse codes intemally at the BIOS (Basic Input/Output System) level. The key advantage is that it replaces bulky extemal drvices. it also provides a mechanism for switch input that does not occupy any of the standard input ports. 2.5.5 Software KEI and GIDEI Software-oniy KEIs became possible in the late 1980s as cornputers becarne more powerfil. Initially. software solutions for text-based operating systems had to ovrrcome some technological hurdles of simultaneous operation of an application and access software. Demasco and Minneman ( 1 986) proposed using a rnulti-tasking operating system to display an on-screen keyboard in one window and the target application in a separate window. Gorgens. Brrgler. and Gorgens ( 1990) employed a terminate-and-stay-resident program to display an on-screen keyboard over top of the application. Gunderson and Vanderheidrn ( 198s) drveloped a multiplexing approach for pointing device input where the on-screen keyboard was visible and the application suspended while inputting. Keystrokes were entered into the application that became visible when the user pointed off-screen. In al1 of these systems. switchrs. and altemate keyboards and pointing devices are attached to a non-standard connrction box that plugs into some input port (Figure 2-17). Software GIDEIs becarne popular with graphical user intertàces (GUIS). Schoenberg & Hallsck ( 1987) described an on-screen keyboard for the Macintosh OS that displayed an on-screen keyboard (~e~~ouse") which transparently cntered text into an active application. It demonstnted an important design feature by allowing a user to directly manipulate the GUI interface and type with a single pointing device. Since input was lirnited to pointing devices mouse emulation was not relevant. A more flexible access device is the K~:NX"which offers a full range of direct selection methods, scaming on-screen keyboards, and switch encoding methods for the Macintosh OS. WestTest Engineering Corporation Bountiful. UT -- University of Utah. Salt Lake City. UT -' Don Johnston Incorporated. Wauconda. IL Standard 1-1 1-1 Computer Switches 1 Keyboard OS r- Connection w Access Box Alternate Messages Keyboards Figure 2-17: Transparent access through keyboard and mouse emulating software that directly injects keyboard and mouse operating systern messages. Implement hg so ftware-on1y solutions introduces some problems that are not of concem wi th extemal GlDEIs (Browniow et al, 1990a). One issue is the difference in the user's perception of the behaviours of an on-screen keyboard as opposed to a window. Thrsr behaviours diffrr from standard designs for windows. but are expected by the user (Shein. 1991b: Shein et al. 1994). For example. the target application should be 'active and in focus' to recrive keystroke input. yet the keyboard should be on top of the application and respond to device input. There are also timrs whrn the on-screen keyboard should behave like a window and have focus. tg.. to size. move or access its menubar. However, as soon as the user wants to type. the target application must regain focus. Because the user expects these two modes of behaviour. intuitive switching between modes must be supponed. This author devised a technique of 'seamless mode switching' (Shein et al, 1992) by breaking GUI conventions in the usability design of the W~V~K"(Figure 2-18) on-screen keyboard that accomplished these behaviours. W iViK was used as the access system for this research. It permits input with any pointing device or scaming with one through five switches and supports al1 of the scaming capabilities described previously (see Section 2.2). " Prcntke Romich Company. Wooster. OH J My Cornputer Nctwork WiViKfY enables you to type with any Neighborhood pointmg device and 1 to 5 switches. 4 l nbox Figure 2-18: WiViK on-screen keyboard. 2.6 Review of Mouse Emulators 2.6.1 Keypad Mouse Emulation Along with keyboard accommodations, the Trace Research and Development Crnter (Lee and Vanderheiden, 1987: Novak, Schauer, Vanderheiden & Borden, 1994) developed a merhod of using the numenc keypad to emulate the mouse, called MouseKeys. MouseKeys is designed for people who use mouthsticks, headsticks, or single digits to type, and for whom an altemate pointing device is not feasible. Such people may have quadriplegia due to a spinal cord injury, or may have limited strengh and range of movement in their hand due to muscular dystrophy. MouseKeys is now incorporated in Windows 95 and Macintosh OS. Figure 2-19 illustrates the rquivalent keys that may be pressed to emulate the pointing device actions with the numenc keypad. Holding dom a direction key (7. 8,9.4,6. 1.2.3) will move the screen pointer until the key is released. The rate of movement is proportional to the time the key is held. staning out slowly and increasing untii a maximum speed is reached (which is counter to pointing movements). Tapping these keys will move the screen pointer one pixel at a time. Tapping the 'Y key will emulate a single-click of the button: tapping it twice in quick succession will emulate a double-click. The '0' key functions as a button down (latch) whilr the '.' hnctions as the 'button-up ' ( release). OEnter Figure 2-19: MouseKeys on the numeric keypad emulates a pointing device. MouseKeys may be difficult for some people because the normal rye-hand coordination associated with the mouse is not present. It may be difficult for such users to hold down a key while looking at the computer screen. Often. their anention is focused on the keyboard and they must release the key to look up at the screen and thrn continue tapping'holding the direction keys. This can require rnuch effort and shifiing of attention. Individuals who have cerebral palsy or another condition that impairs motor control may experience dificulty in releasing the direction keys without overshooting the target. Tasks such as selecting menu commands are often more easily accomplished by entenng the key equivalents to those commands. if they exist. but at a cognitive cost of remembering the keystrokes. Interestingly, one group of people who have gained a new tool in MouseKeys are graphic designers who can now nudge =raphic elements pixel-by-pixel with the keyboard. 2.6.2 Switch-Based Mouse Emulation Switch-based mouse rmulation is sirnilar to MouseKeys. Instead of keypad keys. the user intrracts with individual switches or multiple switch devices. such as a joystick. where each switch is assigned to a specific direction. These switchrs are comected to an extemal mouse cmulator which in mm connects to the standard mouse port. As switch activation is maintained. the screen pointer moves in the associated direction. Here. timing of activation is translatrd into movement. Commercial devicrs (s.3.. ~h4ouseEmulator.MouseMover) include adjustable timing so that the speed of the screen pointer can Vary. A separate switch is assigned to be a mouse button. Similar problrms with shifiing focus and attention bctween the switch and screen. as with MouseKeys. may occur (Brownlow et al, 1 989a). 2.6.3 Non-Transparent Command-Based Pointer Prior to the smergencr of GUIS as the standard user interface environment. research had bren undenaken by this author to invrstigate alternate access methods that would allow individuals with disabilities to control a screen pointer. Some of these concepts are used within this thesis. Shrin et al ( 1985) first studied positioning and moving a scrern pointer in a Logo drawinz environment by explicit movement commands genented on a front-end computer confipration. Logo is a programming language drvrloped to hrlp children leam logical and spatial concepts. An on-screen keyboard of symbolic commands (Figure 2-20) was specifically designed for child usrrs who were severely physically disabled and non-speaking (Pearson, et al, 1984; Pearson- Hirdes, Lee. Shein and Pames. 1985). The user could scan and select commands using one of several scaming methods. Commands were displayed in Blissymbols (Bliss. 1947). a graphic syrnbolic communication system that the children used to communicate. Figure 2-20: Advanced-level Logo front-end on-screen keyboard displaying Blissymbol commands (left) and back-end screen displaying Logo application (right). This implementation was an early rxample of achieving access to manipulation of a screen pointer by providing more than directional arrow commands within the altemate interface. The user could direct the cursor to any location by programming sequencss of movement and direction commands. Multiple movements were implemented through a repeat loop. These srquences could be stored and latrr recalled in a single selection. For example. the following Logo program draws a square: To Box Repeat 4 [Forward 100 Right 901 End Box Shein et al ( 1985) reponed that a drawback to this system was its requirement for the user to understand numbers and spatial concepts in order to move the pointer. However. it was designed in such a way that users could explore and leam about these concepts. Pointing access was achieved through pre-planning. mental spatial movements and delegation of commands rather than by demonstration as with a pointing device. 2.6.4 Non-Transparent Scanning Screen Pointer Shein et al ( 1984) described a sc~mingscreen pointer in a non-GUI environment that was the foremnner of current scanning screen pointerdmouse emulators. Access was non-transparent and was limited to a drawing software application called PIC-MAN (Shein and Milner. 1985) (Figure 2-21). Figure 2-21 : Typical PIC-MAN screen layout with a simple drawing. This program displayed a Logo-like drawing environrnent with a single line of commands in Blissymbols (forward. back. lefi. nght. pen up. pen down. pen colour. arcicircle. and undo). These commands were automaticaIIy scanned for selection by a single-switch. The drawing pointer rotated and moved along a straight-line pathway in scanning increments. This idea is similar to the way in which young children draw or drive an electnc wheelchair. Le.. by moving in somr direction and then stopping when they decide that they have reached the end. It is important to note thai in this drawing task. the pathway of the screen pointer created the drawing. The first selection of a movement comrnand started the screen pointer (arrowhead) scanning in the selrcted direction. If the right (clockwise) or left (counterclockwise) directions were chosen, the scrern pointer rotated in that direction. (This is in contrast to standard screen pointers that remain in a fixed upward pointing direction.) A second activation stopped the pointer. and the comrnands were scanned again. Thus. the scaming extended frorn the on-screen commands into the drawing in an integrated fashion. An innovation was the use of a linr extending fiom the tip of the pointer indicating the heading or pathway in which it would move once rotation stopped. This enabled users to more easily point directly at the target. Othenvise. multiple movement steps would be required to reach the target. An issue arising then, and remaining still with scaming screen pointers, is spatial confusion when the pointer faces down. It may not be clear to the user that selecting forward will move the pointer down because fonvard is generally associated with an upwards movement on a cornputer screen. 2.6.5 Transparent Scanning Screen Pointer In GUIS, transparent mouse emulation for scaming usen has generally been accomplished through a scanning screen pointer. It involves moving the GUI screen pointer and performing button actions (click, double-click, button down, or button up) through scaming software. Button actions are generally chosen as keys within the on-screen keyboard. Applications respond as if a standard mouse was comected. Two general styles of scanning screen pointer have evolved: 1. HorizontaWertical Scanning. The first style is based on scanning along orthogonal directions (horizontally or vertically) until the target is reached. Thus. the user must choose at least two directions. Choosing a direction can be donr through an on-screen keyboard direction key (up. down, left, right), or a screen pointer that rotates in 90" incremrnts (Fi,oure 1-22) (K~:NX''). Afier choosing a direction. the screen pointer scans in that direction. Altemately. a horizontal line may scan top-to-bottom across the screen until it intersects the taget: then the pointer scans from lefi-to-iight. until the target is reached (~ross~canner'~). Figure 2-22: Scanning screen pointer with horizontal and vertical movements. 2. 360" Rotational Scanning. The second style utilizes a 360' rotating screen pointer that is stopped when it points at the target (Radar~ousr', Revolving ~oors'"WiViK 2 scan2").The cursor then scans along the chosen heading until the target is reached (Figure 2-23). In some prodiicts a Line is drawn fiom the tip of the pointer to help point more precisely at the target. -'Don Johnston Incorponred. Wauconda. IL '"1 Cooper and Associates. Dana Point CA - Words+. Inc.. Palmdale. CA " Madenta Communication Inc.. Edmonton. AB " Prentke Romich Company. Wooster. OH Figure 2-23: Scanning screen pointer with movement along user-selected heading. Current clinical opinion (Swain, 1996. persona1 communication) suggests that scanning top-to- bottom. and left-to-right across the screen is easier for users. Such a systrm does not rrnulate the movements associatrd with a mouse. Instead, it emulates the task of selecting coordinates. This is easier because the user is only concemed with selection. not movement and al1 scanning is down and across to the right. A revolving and scaming screen pointer on the other hand rnay cause spatial confusion when pointing downwards (Shein and Milner. 1 985). In both cases. selecting a point is a three-step process: selecting a vertical position then a horizontal position: or, selecting a heading then a distance: then selecting a button click. Most scaming screen pointers have two inconsistencies when compared with the way on-scrern keyboards are scanned. First. although the screen pointer rnay step through some rotational incremrnt (usually 90') it then rnoves smoothly across the screen in a continuous fashion. Second, the screen pointer does not highlight successively smaller groups of items (angles and distances). Recognizing these inconsistencies change the scaming task for the user. this author designed a scanning screen pointer within WiViK that highlights the angular steps ahead of the heading line (Shein et al. 1992b). The user first chooses a rotation command, then the pointer begins rotating in -15" increments while highlighting the next 45" arc (Figure 2-24). Subsequent switch activations reduce the arc (1 5". 5". 1") until the target is intersected by a straight line. Similar to scanning the on-screen keyboard, the user attends to the target. and activates the selection switch whenever the target is highlighted until the correct heading is selected. The pointer then moves along that line beginning with large steps, then smaller steps until the target is reached. This author specified a set of comrnands for use within WiViK key definitions that are similar to the GIDE1 codes suggested by the Trace Center. WiViK translates thcse into appropriate operating system messages that get injected directly into the message Stream. Since a screen pointer does not have a heading associated with it, as it always points upward. WiViK separately maintains heading information. To rnove the scïcen pointer, WiViK translates the movement along the heading into the appropriate XY coordinates. Button actions follow standard messages. Figure 2-24: Scanning screen pointer with rotating arcs highlighting in WiViK. 2.6.6 Scanning Screen Pointer Enhancernents Access developers have recognized for some time the dificulties with precisely positioning the screen pointer over targets. Therefore, they have enhanced scanning screen pointers to reduce users' efforts when perforrning certain tasks (Cook and Hussey, 1995). For example, to make selection of menu commands easier, the scanning screen pointer in one product uses mouse macros to jump to the menu bar with one selection in the on-screen keyboard. The pointer then scans across the menu bar. When the pointer is over a desired menu. switch activation drops the menu down and the pointer scans down the menu. When the pointer reaches the bottom of the menu. it retums to the top if a menu selection is not made. The same product also supports scaming across previously tagged locations to quicken access. This depends. however. upon someone (generally not the user) defining such locations. Lewis and iMarsden ( 1993) proposed several enhancrments to a scaming pointer. To reducr the demands of switching attention back to the on-screen keyboard to select a button action. they proposrd that likely options should be displayed once the rotating screen pointer stops. Vanous button and movement actions are presented as icon representations one-at-a-time in sequrnce at the screen pointer tip. They suggested that this eliminated attention shifis between the on-screen keyboard and the pointer. The intention was to reduce errors and waitinz time. Lewis and Marsdcn also proposed to have the screen pointer scan across key GUI window controls. such as a window title bar, scroll bars and control boxes. or previously rnarked locations. Positioning the pointer over one of thess objects can othenvise be quitr difficult. A final enhancement was to have the pointer jump to a window control as it passes nearby as if by magnetic pull. If the user did not indicate to stop by switch activation, the pointer continued dong its previous path. Al1 pnmary GUI window gadgets that are known to the access system could have this 'magnetic' attraction to a moving screen pointer. Moynahan and Mahoney ( 1995, 1996) proposed a novel scaming screen pointer concept that potentially allows the user greater control over the task of moving to a target rather than rnoving the pointer along a particular direction. They employed an intelligent agent to facilitate control. Instead of sprcifying any directions, the user initiates pointer movement. from which the agent infers where the user might want it to go. As the pointer moves, the user can stop rnovement with a switch activation if the pointer moves away From the target. wherrupon the agent re-evaluates the situation and Stans the pointer moving towards another target. This interaction continues until the desired target is reached. These researchers demonstrated that usen could reach a limited set of four targets faster and with less activation than widi MouseKeys. 2.7 Review of Text Selection Methods Text editing is one of the rnost common computer applications. Within the overall contrxt of tcxt editing there are many tasks that the user must carry out. Roberts and Moran ( 1982) presented a taxonomy of such editing tasks that is usefùl for cornparhg systerns. Of those tasks. it is the canying out of "core" tasks which is of significant interest fiom an accessibility viewpoint because these are the most fiequent tasks. Core tasks apply operations (insrrt. delrte. replace. move. copy. transpose. split, merge) to basic texr objects (character. word. line. sentence. paragraph and section) (Roberts and Moran. 1 982). Integral to these core tasks is the moving a text cunor to a discrete insertion point or across a text object to indicate selection of that object to then operate upon it. This positioning is different from othrr GUI positioning tasks because it involves a text cursor that is indeprndent of the screen pointer. The text cursor can be moved with keystrokes or by direct placement with the mouse. Card, Engl ish and Burr ( 1978) descnbed expenments that cornparrd different methods of pointing to a specific location using step keys (arrow keys). text keys (character. word. iine and paragraph keys). a mouse, and an isometnc joystick. The mouse was clearly the fastest with users (who were able-bodied) and step keys the slowest. Even when step keys incorporated repeating, they were slower than text keys because the total number of keystroka was higher. Brownlow et al (1989ab) suggested that the mouse advantage does not necessanly cary over to users with disabilities who use scanning access systems. Repeatedly scanning to movement keys within an on-screen keyboard as a means of positioning the text cursor was cumbersome and taxing on the users because of the large number of selections required. Controlling a scanning screen pointer and selecting button actions in an on-screen keyboard was similarly problematic. It had been obsewed that many users simply did not edit beyond using the cBackspace> key. Shein et al (1 990) descnbed an exploratory study of an idea to consider the text area itself as a selection set so that it could be scanned directly. This followed this author's recognition that a key problem with scanning screen pointers was that moving the screen pointer was secondary to the task of moving the text cursor or identiwing the insertion point. Scanning the text allowed blocks of text to be selected like any other item: the text blocks become a selection set of paragraphs, sentences, words. and charactes. This was a scanning paradigm that was already familiar to the user. In doing so, it had been envisioned that scanning text could become as routine as scaming an on-screen keyboard. Card, Moran and Newell ( 1979) described such a ski11 as a "routine cognitive skill" which is familiar and repetitive. It is mastered with practice and training but yet it requires thinking because of task variation and induced errors. Two prototypes of a scanning text editor and on-screen keyboard were prograrnmed for rvaluating this concept. In the first prototype, the user scamed blocks of text to place the insertion point. The second prototype attempted to reduce the scaming demands by taking advantage of the nature of block scanning. Instead of block scanning to a single insertion point. users were asked to employ the information associated with the beginning and end points. and the extent of the block. At any point the user could stop the scanning and select the current block. Thus, without having to define both begiming and end points, the user could select text for sditing in the standard block sizes. Individual paragraphs, sentences. words. and characters could then be directly selected. Having selected a block, the user could also choose to set the insertion point: before the block. ovrr the block (so that hrther typing will overwrite it). or after the block. This second prototype. however, was found to be confusing because the usen had to consciously think about the three piecss of information relating to blocks of text (beginning, end. and extent). Scveral key ideas were suggested by this text scanning research. First. block scanning combined wi th the efficiencies of text key movements resulted in faster and less demanding access. Second. scanning the text offered a feeling of 'directness' to users. Third. users could transfer the concept of scaming in an on-screen keyboard to scanning successive blocks of text. Founh, users understood the idea of scanning blocks that reduced in size down to a single charmer to set the insertion point, but they had difficulty using the text block to set the insertion point with respect to it. Last. an on-screen keyboard could initiate and control sca~ingthe text. 2.8 Summary GUIS have sirnplified the use of cornputers for many people by employing direct manipulation. mis concept remains relevant in designing alternate access systems even if a pointing device cannot be used and provides a basis for understanding user demands and difficulties. Particular dificulties anse when switch-based scaming access methods are employed. Many permutations of scanning configurations are possible through V~~OUScombinations of switches and patterns of scanning movement. Without describing every possible scanning configuration. Vanderheiden ( 1985) presented a model in which any selection-based access method may be constructed. Thus. while a designer may create a novel scanning arrangement. al1 access methods can be described in terms of Vanderheiden's model. More genrral models of access have been proposed. Al1 incorporate the primary concept of transparent access such that a standard computer and application can be used without modification. Certain riements of the input/output stream can be replaced or modified such that user actions are interpreted in a standard fashion by the computer. Most models are primarily concerned with achieving standard keyboard and mousr input. These have been implemented in access systems begi~ingwith keyboard emulating interfaces (KEIs) and rvolving into general input device emulating interfaces (GIDEIs) which have added mouse emulation. MacDougaIl et a1 ( 1 988ab) presented the most detailed model illustrating the concept of a mu1 ti- component access system. This model descnbed the access process through a sena of translation modules from physical actions to injecting underl ying input signals to the computer. These modules are independent of one another such that they can be individually replaced or modified and access will be maintained. MacDougall et al recognized that the input signal should ideally be more than just keyboard and mouse signals. They proposed that designers consider using standard input primitives, but this was not practical at the time given current operating systern design. Adams and Abbott ( 199 1 ) had similar concems and suggested a third signal, in addition to the keyboard and mouse, to input standard operating system messages. Emulating the actions of a mouse to control a screen pointer through scanning became a concern as GUIS gained popularity. Earl y research demonstrated that an indirect access system can be designed to move the screen pointer by selecting direction and distance commands. A scaming screen pointer was fint demonstrated in a drawing program and was Iater extended for general accrss to al1 GUI applications in commercial access systems. This has become. more or Iess. the standard scanning method for manipulation within a GUI. Developers have recognized that moving the screen pointer can become a significant task in itselE Therefore. they have devised methods to speed up movement to the target. The solutions drveloped to date involve 'jumping' the screen pointer to GUI objects of inierest (e.g.. menu or window button) so that the user does not have ro move the screen pointer first to that location. Some initial research has been camed out on the use of an intelligent agent to reduce the nerd to jump to a potential target before rejecting it. but only with a small set of objects. A novel approach was studied by this author to specifically address the issue of selrcting trxt which is integnl to many computer applications. Instead of using a scanning screen pointer. scaming was directly applied to the text. Although the results of this pilot study were limited. the potential for a task-transparent scaming approach was identified. This provided the impetus for the current thesis research. 3 Task Transparency : A New Design Approach 3.1 Introduction This chapter outlines the proposed task transparency mode1 (building upon the concepts identified in Chapter 2). and applies it to the task of selecting tex:. It begins with a summary interpretation of the literature highlighting the specific deficiencies of the current approaches to alternative access and the related technology. This is followed by a description of task transparency from an overall perspective and with respect to selecting text through a scannine access method. I then apply this approach to the task of selecting text and describe its implrmentation through a nurnber of proposed strategies. Recognizing that the application of scanning to text can create situations where groups with many items (e.g.,words in a linr) are scannrd. a stntegy for reducing scaming time. called overdrive scanning. is descnbed. The evaluation of these strategirs is discussed in later chapters in which new knowlrdge is sought to better understand the user interaction issues that arise. 3.2 lnterpretation of the Literature The ernergence of GUIShas simplified the use of cornputers for rnany persons. Direct manipulation within a GUI has made this ease-of-use possible in conjunction with a mouse or other pointing device. However, the benefits are only realized when 'directness' is maintained. Such directness is achieved through the use of a metaphor, brevity of actions, and the mirnicking of tasks to physical actions through the operations of the input device. It remains a challenge to design access systems for scaming users that maintain the benefits while providing alternatives to the physical manipulations. To date, the vanous implementations of transparent access that have been developed differ only in terms of where the access system physically sits with respect to the computer and application. They al1 follow the general pnnciples of translation suggested by MacDougall a al. and within that, the model of selection by Vanderheiden ( 1985). They also maintain a focus on device rmulation following the genenl assumption that the input task is to generate both keystroke and mouse actions. Only the mode1 suggested by Adams and Abbott ( 199 1 ) explicitly addresses channels of input other than the keyboard and mouse. Nonetheless. the transparent accrss models offer an important rneans of communicating control between the user and the computer. The model of human-computer interaction suggested by Nirlsen ( 1986) is useful to understand the pitfalls associated with access models. The GIDE1 models only drscribe the visible portion of the interaction. and designers ofien neglect the invisible translations. With direct selection methods this is not as serious a concem. Here. the physical selections directly act on the alphabetic bits of information (cg.. keystrokes. mouse coordinates) and in some cases the lexical tokrns (e.g..words. commands) through input mapping. These physical acts combine syntactically in such a way that the intended tasks of the user are camed out. However. when indirect selection is employed. the interaction model is stacked with the selection method itself haïing its own layers of interaction. Here, the invisible layers of setring goals. tasks and understanding the semantics of both the application and the indirect selection interaction can conflict or confuse the user. The visible portion of the indirect selection method does not match the equivalent portion of standard input. Yrt, the user must ofien keep standard operations in mind so that they achirve functional equivalency. This problem is more apparent with altemate access approaches that emulate the mouse through scaming. Shein et al (1 985) demonstrated that children with severe physical disabilities could leam to program sequences of cunor movements to draw. The required spatial knowledge and the many commands to be selected, however, made this approach too slow and diffcult to be generally practical. Nonetheless, it had certain qualities associated with direct manipulation. The programming of movement sequences for later reuse helped provide brevity to some interactions. Semantic directness was partially achieved through the comrnand selection approach which was similar to delegating othen to perform tasks on your behalf (Brownlow et al. 1990b). but the use of numbers detracted from the overall directness. The scanning screen pointer in the PIC-MAN drawing software achieved both semantic and articulatory directness lacking in the Logo command approach. The scanning pointer required minimal and brief physical and cognitive effort. it followed the metaphor of a child drawing. and it was accomplished through consistent scaming. Within the limitcd context of a drawing program. the scaming pointer approach worked well. However, it is suggested that this does no< hold true for mouse emulation where the pathway of movement is no longer important. When a person uses a scanning screen pointer. the movement of the pointer becomes the dominating task yet the operation of moving the screen pointer ofien has no bearing on the undrrlying task. Although access is achieved. directness is lost in many ways. The standard mrtaphor of an office desktop may be quite foreign to someone who has never worked in an office. The repetitive movement and attention switching between the scanning screen pointer and the on-screen keyboard reduces brevity. The screen pointer coordinates are separated and umelated to the data beneath it except by visual matching. Users perceive themselves as 'dnving' the cursor and must be concemed with srelring rather than pointing directly at the desired end location. The actions associated with pointing do not mimic real capabilities of the user. Pointing drvices require control over positioning, direction of movement. speed of movement. and button activation (clicking. double-clicking, holding). Someone who can only activate discrete switches has no control over positioning or movement. Enhancements to scanning screen pointers that have been devised offer some brevity to the access, but do not relieve understanding concepts of pointing and moving. A common deficiency with the enhancements is that they are difficult to apply to dynarnically changing objects or large numbers of objects. In particular, no enhancement has been proposed that enable the user to quickly position the screen pointer over a specific location within a text field, a core task within text editing. A scanning screen pointer is awkward to use to access text because it loses al1 of the advantages of reai mousc input. When a screen pointer scans. it steps across the screen limited by a scan intemal according to the user's ability to respond with switch activation. The number of steps is dependent upon the distance the screen pointer must movr from its starting location to the desired point. This distance is constantly varying depending upon the current screen pointer location. It is without direct reference to the text beneath it cxcept by visually matching the screen pointer location to the desired text cursor location. Fine control is required to stop the pointer at that precise location. Consider the cases illustrated in Figure 3-1 and Figure 3-2. The user task is to place the insertion point at position B rathrr than its current position A. Figure 3-1 : Task of rnoving screen pointer from point (x,. y,) to (xBVyB) aa-z aliquefi eraP~:!&t~ar. TB Figure 3-2:Task of rnoving screen pointer from point (xp,y2) to (xBVye) Althouçh the user task is the same in both cases, the user faces two different movement tasks with a scaming screen pointer because its location is inconsistent. In some instances this movement may be small. while large in others. This situation forces the user to focus on movernent. and it becomes the primary task. In contrast, an able-bodied user could use a mouse to move the screen pointer with ease from any location with little thought. Selecting on-screen keyboard movement keys is also unwirldy because it requires much key selection and switch activation. Using text keys (e-g., word, pangraph) rather than step keys (Le.. arrow keys) can help the situation as the text cursor will then move in text units rrquinng fewer steps. An advanrage of text movement keys is that they directly act upon the text cursor. Editing remains curnbersorne. however, and many users simply do not edit. As an initial attempt to address this limitation. this author developed and studied two prototypes that took advantage of the notion of text movement keys and directly applied scanning across text (Shein. 1990). This work lrad to a number of key ideas that have influenced this thesis. 3.3 Task Transparency and Scanning The original definition of transparency does not descnbe how an alternate access systern should be desiçned. Rather. it only States that any modifications shoiild not be detected by the standard interface. It has nevertheless been interpreted in terms of drvice function or device transporenc-*. Le.. any alternate access system must provide the fûnctions of the standard input devices such that the application responds as if those devices were comected. This is a case of design following hnction. It assumes that if the function of the device is available. then user access is assured. However. only when the function matches the user task, e.g. for drawing. is directness possible through device transparency. A rask transparerzq approach that directly applies the accrss method to task objects should provide a greater feeling of directness to the desired task. For direct selection methods where the keyboard and mouse are replaced with devices requinng minimal user attention. task transparency is equivalent to device transparency. In this case, the device operation is transparent to the standard input tasks and the user directly caries out those tasks. This is always the first attempt in providing cornputer access for someone with a disability. As soon as the user has difficulty with a device and must focus on its operation, then the underlying tasks should be identified so potential alternatives to accessing those tasks can be considered. The potential impact of those alternatives on overall usability and demands must then be determined. If a scaming access method is used, it is suggested that a task transparent approach should always be considered. The kryboard and mouse input charnels are not to be ignored even if a task-transparent approach is adopted. These channels remain as camers of information. Additional information-canying charnels should also be considered such as operating system messages delivered through some internai bus or message queue. Once a task is descnbed in terms of its inclusion within the access system, its implrmentation is a matter of practicali ty and whatever signal channel is most appropriate or available can be used. The user should not perceive the underlying messaging: the end result should appear the same. no matter which charnel is used. For example. if the task is to choose an icon from a group of icons. that group becomes a selection set within the access systern that may highlight each one sequentially with item scanning. Linked with each item in the selection set would be a keystroke equivalency. a set of coordinates. or a selection message that would be conveyed at each scan interval. This is made easier within operating systems that encourage user interface designers to group related objects and allow a standard set of keystrokes to move between objects. Thus. once a group is identified. a single keystroke. such as Gab> may be used to move fiom i rem to item. It is usehl to consider the virtual communication protocol suggested by Nielsen ( 1986) to define the layers of interaction associated with the user tasks. In doing so. it should be recogized that tasks rnay be accomplished through a number of different means rven with a consistent access method. For rxample. consider a task conceming a target object with some value that varies (e.g.. texr cursor location, window dimension. and document view). Depending upon the semantics that the designer might consider, a task transparent approach rnight set a new value by havins the target object's value scan (move) in some logical increment, or altemately by scanning across its range of value such that the end value becomes the target for selection. If the task relates to selecting a non-varying object, then scanning can be applied across the set of objects containing the target object. Altemately, that object may be incorporated directly in the on-screen keyboard if i t is frequently used and if i t does not add substantially to the keyboard selection set. In this and the previous situation. any naniral arrangementlrelationships of objects can be used to advantage in establishing scaming group dimensions. The designer has the hrther option of having the scanning proceed sequentially from large to small steps. or having the scaming proceed as a series of user-detemined steps. The former is similar to traditional group scaming and the latter is similar to item scaming. These variations in operation or strategy are a foreseen difficulty with task transparency. Attention must be paid to rnsure that whatever strategy is adopted can be applied with some consistency across di fferent tas ks. However. it was not known which particular stntrgy should be applied and what would be the impact on usability for various desips. To appropnately design effective scanning systems to accomplish such tasks as text selection. knowledge is required to understand specific usability and demand issues. Such performance knowledge is also usefül to detennine the value of a particular strategy. As reponed previously (Shein et al, 1990). expected performances with 'efficient' scaming text strategies do not always correspond to improvernents in actual user performance. Current guidelines for scanning systrms are quite broad (sre Appendix J) and are insufficient to fûlly guide the design of task-transparent scanning strategies since they have only been demonstrated usefui with on-screen keyboards where the selection task is straightfonvard. This is not necessarily the case for scanning across a large dynamic selection set such as tex Vanderheiden's mode1 remains usehl for the quantitative cornparison of newly desipsd methods but it does not identifi al1 of the usability issues nor suggest an appropriate msthod for a particular task. A number of questions anse in the application of task transparent scaming that are addressed hrre by evaluating vanous strategies applied to the task of text selection: How should task scanning be implemented? How effective are different stntegies (e.g., moving versus selecfing an object or value) in terms of usability, user demands, performance, and errors? How effective is group sca~ingversus item scanning when applied to tasks? How does the user recover fiom selection errors? Considering the scaming dimensions are variable in a dynamic set (eg,text object sizes), how might a user reduce scanning time when the number of items in one grouping is large? 3.4 Applying Task Transparency to Text Selection 3.4.1 Text Selection Task Selecting an irregular section of text (i.e.. not a complete word. sentence, ~ara~gaph,section. etc.) for rditing is a four-step process: identifying the begiming point; initiating the selection: identifiing the end point; and stopping the selection. Identifjk~gthe beginninç and end points within a text field are rquivalent tasks. This involws altering the coordinates of the insertion point in terms of its position within the tent field. The insertion point is visually represented by a text cursor that movrs with respect to the textual elements. Considering that this involves changing an object's value within a large range (rqual to the nurnber of characters in the text tield) it is appropriate to apply scanning within the text field. On the othrr hand, initiating and stopping the selection are fiequent discrete tasks that are best represrnted as one on-screen kcy thar toggles to represent the two States. This aspect of the selrction task is straightfonvard: therefore. attention is paid to the former task. Tliçre are two views that can be taken to identify the insertion point: ( I ) move the text cursor by scanning across the text objects to the target insertion point: or (2) scan the text by highlighting it to select the targçt insertion point. In both cases. text objects (paragraphs. lines. words. and characters) are natural scaming group sizes rather than just step keys (arrow keys) because of their efficiency (Card. English and Burr, 1978). Vanous scaming strategies incorporating these views were evaluated in this thesis. These are described in Section 3.4.4 below. Potentially. different size iext object sizes could be used. such as sentences or groups of words versus lines. There is a practical argument for using sentence increments because these are more likely to be selected for editing than lines. However, there is an equally valid argument for using lines rather than sentences because sentences ofien begin and end midway through a line. This increases the visual-perceptual demands of finding the text cursor. Also. it may take longer to scan through al1 of the words in a sentence than across a line. Word processors usually follow the latter argument and provide keyboard support for moving by characters. words, lines and paragraphs. Thus. it becomes a practical dificulty for an access system to work in sentences because there is no mechanism to move with respect to sentences. Some sensing of the text would be required to acquire knowledge of sentences. The efficiencies of block sizes may be debated based on eficiency crossover points suçgested by Kulikowski ( 1985: see Table 2- 1. pg. 20). At a selection set size (compnsing text chancters) of 3 3 1. he suggests that 5-dimensional scanning becomes efficient. This wouid correspond. in practical terms. to a typical four to five line paragraph. Thus, in larger paragraphs. it might make sense to consider an additional sentence grouping. However. it would create an inconsistency if scanning went by sentences in some cases and not in others. At some point. users must indicate that they want to shifi scanning fiom the on-screcn kryboard to the text area. The only selection option available to a user while scanning the on-screen keyboard is to select a key to initiate the transfer. A single kçy to begin scanninz the iext in a forward direction would be insufficient because the target point rnay bc behind the current insertion point. Therefore. keys for initiating both forward and backward scanning are required. Funher. since only the user knows the distance from the current insertion point to the target point. and it may Vary in distance, scaming should be initiated at any of the possible movement increments. Thus. each movement increment requires individual keys. Once a selection in the text area is made. scanning should resume in the on-screen keyboard because there are no other selectable objects in the text area to indicate a shifi back. This allows the user to choose text scaming in a different direction or increment, or to perfonn another task. Switching between scanning the on-screen keyboard and the text can thus be searnless. The starting point for scanning within the text is an issue of concem. Should the scanning begin at the current insertion point, or should it start at some arbitrary point such as the upper-left hand corner as it does in the on-scrern keyboard? Within the experiment carried out in this thesis. a decision was made to place the insertion point initially at the upper left-band corner and begin scaming fiorn that point. (In a real situation. it would be at the last text insertion point.) Afier the text insertion point was positioned at the begiming of the texr block, scanning continued from that point forward to the end of the text block. 3.4.2 Keyboard Channel as Information Carrier Transfemng scanning From the on-screen keyboard to the text area can be accomplished by using the keyboard charnel as an information camer if the target application can appropriately respond to the keyboard messages. In this thesis. the WiViK on-screen keyboard was used to enter keystrokes into the text field in a repeating fashion. Thus. the user perceived the text cursor to be scaming. Keystrokes offrred a practical means to ensure transparency. A repeat structure was added to WiViK to achieve scaminç via krystrokss that movs the trxt cursor. This was selectively appl ird to those text keys with associated scaming ( fonvard and backward movrments in character. word, line and paragraph increments). The structure was similar to the repeat structure used in the previous Logo study (Shein et al. 1985). However, an infinits repeat loop was used. An immediate issue was how to stop the scanning. Since switch activation was usrd to select a key. it was logical to activate the switch again to stop scanning. At rach of the text keys. the following structure was used: For example, to have the text cursor scan fonvard by words, the following rnapping was defined at the 'word' text key. (Note: the terms BeginRepeat and EndRepeat are used to define the repeat loop and may be replaced with the shorter forms BegR and EndR in WiViK). When this key was selected, the Not al1 text key movements required associated scaming. In particular, 3.4.3 On-Screen Keyboard Special definitions (mappings) of the on-scrern keyboard were necessary to suppon the vanous scanning operations. Although the underlying mappings Vary with the different operational strategies, the keyboard display can be constant. To reduce the time taken to scan the on-screen keyboard to choose the text scanning keys. a separate 'page' distinct from the standard tsxt rntry page (Figure 3-3) was designed to hold just the relevant text movement keys. This page can br linked to the text entry page with a single key. Link to text movement keys Shift 1 ABC 1 Ctrl 1 Alt 1 PrSc 1 Ins / Del 1 Figure 3-3: WiViK on-screen board text entry page with link to text movernent keys page. Pnor to evaluation, it was not feasible to arrange the keys based on frequency-of-use to minimize scaming time since usage was not known. Therefore, a common layout was designed (Figure 3-4). This layout incorporated movement keys common to al1 strategies including: characrefi. words. lines, and para_graphs fonvard and backwards: end. home, page down. and page up. A ky to stan extending a selection across a block was also included. This key roggled to stop the selection. An additional 'Stan' kry was used only within the expenment discussed in the nçxt chapter for initiating trials. are keys for moving by characters, words, lines, and paragraphs respectively; these Vary in function according to each strategy are keys for moving backwards by characters, words, lines, and paragraphs respectively; these Vary in function according ta each strategy The remaining keys are common to al1 strategies: 'move the insertion point afkr the ast character (End) and before the first (Home) O 2 scroll th2 vie* up and down by one page and move the insertion point up Io the top line of the visible page . (extend mode) togples an extend mode. For exarnple. when the extend mode is first selected. text will be selected based upon the next rnovements. Choosing 3 (cursor mode) stops the extend mode. Figure 3-4: Common WiViK on-screen keyboard layout for al1 scanning strategies. 3.4.4 Text Selection Scanning Strategies This section descnbes proposed strategies associated with positioning the insertion point within a section of text using rask transparent scanning approaches. Specific keyboard definition files are provided in Appendix A for each strategy. A standard keystroke strategy of selecting individual text keys to move the text cursor is first described as a basis for comparison. Then two methods of applying scanning to move the text cunor are described. In a scanning text keys strategy. the user chooses text key increments by which the text cursor scans. In the sequential scanning text keys strategy, the text cursor scans through sequrnces of text key increments similar to group scanning. This allows the user to move the text cursor to the target point in one scanning opention. The last text scanning strategy involves srlecring the insenion point. rather than moving the trxt cursor. by scanning the text in diminishing block sizes. 3.441 Strategy 1: Standard Keystrokes The text cursor moves once for every selection of a movement key. The standard method is ro select text keys by scaming within the on-screen keyboard as many timss as necessary to move the text cursor until the targret insertion point is reachctd. Gsnemlly. the user Stans by selecting large movemtnts. followed by smaller movemrnts. often following some plan to reduce the overall number of steps. Within the on-screen keyboard. keyboard equivalency to text ktys are mapped onto individual keys if they are not represented by a single keystroke. e.g.. CCtrlxRight-Arrow> to move ahead by one word, and CCtrlxDown-Arrow> to move ahead by one paragraph. Figure 3-5 illustrates typical individual rnovements of the text cursor. e.g., dom two lines. across three words. and across four characters. The time associated with every move includes locating the text cursor in the text and planning what next to choose (Pi, i = individual text movement) . and selecting the movement key in the on-screen keyboard using row/column scaming (Ki) (Pi + Ki) is the tirne to move the text cursor one step. A delay on the first row scamed is often sufficient to absorb time taken in locating the text cunor and planning. If the user dors not select the desired row in the on-screen keyboard. the user must thrn wait for the scaming to "wraparound the keyboard. bcran-. 1psa.m i'olcr sir amct cûnsrctstuer adry~sc:xc, e1:t P, + Ki ked dlam ncxumy xzbh eï~sncciclnçldi;~r UT làore?: Iclcr? inaga lalrcpan bra; bMpat. ::t wiîi 5x2s ad n;nm -;tn:an Figure 3-5: Strategy 1 : Standard keystrokes to move the text cursor. 3.4.1.2 Strategy 2: Scanning Tert Keys The text cursor scans by one tert key increment (characters, words, lines, or paragraphs). This is repeated with other text key increments until the target insertion point is reached. Here. the scanning method is applied to the task of moving the text cursor in an rlemrnt scanning fashion. This is similar to whrre an able-bodied person might repeat a key by holding it down. When the usrr choosrs a text movement key in the on-screen keyboard. the text cursor begins scanning by that increment. As the text cursor scans, the user tracks it with respect to the target. The usrr stops the scanning with switch activation when the next movement would overshoot the target. Then the user chooses another key. Similar to the standard keystroke strategy. it is to be expected that the user fint scans by larger increments and then successively smaller incremenrs to reach the target. When "extending" a selection, the end point of the selected block appears to be scaming, in which case the user tracks the end of the selection. The advantage of this strategy is that the user does not have to re-select the sarne key nor constantly switch attention between the text area and on-screen keyboard with every movement. As before, the time associated with selecting movement keys includes finding the text cursor in the text, deciding which movement to choose next, and then selecting that movement key using rowicolumn scanning. Figure 36 illustrates typical scaming of the text cursor. eg.. down two lines. across three words. and across four characters. The time to chooss the first scanning movemrnt is similar to Strategy 1 (Pi + Ki), however. the timr between text cursor movements is now only one scan interval (S) except on the first step which is delayed (2s).The dçiay causes the text cursor to pause at the fint character allowing the user to more easily select it without advancing the text cursor. Repeating keystrokes Figure 3-6: Strategy 2: Scanning text keys to move the text cursor. This strategy is rransparently accomplished by mappinç tsxr keys with a single reprat loop of relevant kçystrokrs within the on-screen keyboard. For example. 'scan ahead by paragaphs' is accompl ished wi th the followinç repeat loop. 3.1.1.3 Strategy 3: Sequential Scanning Text Keys The text cursor scans by sequential text key increments beginning with large movements followed by successively smaller movements (first by paragraphs, then by lines, words, and characten) until it reaches the target insertion point in a single scanning operation. Here, the scanning is also applied to the task of rnoving the text cursor. but in a goup scanning fashion. Keys in the on-screen keyboard indicate at which level to start scaming. As the text cursor scans. the user tracks it with respect to the target point. The user stops scanning at a certain level when the next movement would overshoot the taqet. This continues until the target is reached. Thus. any point in the text field can be reached with a single scanning operation. This significantly reduces attention switching between the text area and the on-screen kryboard. When extending a selection. the selcction appears to be scanning in which case the user tracks the end of the selected block. An intrnt with this strategy was to have the user develop a mental model (Rubenstein and Hersh. 1984) such that they felt they were controlling a scanning text cursor analogous to a scanning screen pointer. The advantage over a scanning screen pointer is that rather than scaming both directions and distances, the user only needs to scan distances. With this strateLy. it is necessary to provide a method for users to indicate when they do not want to follow through with the entire sequence to prevent overshooting the target. If users have only a single switch. they nsed to repeatedly activate it to advance through the macro sequences. Alternately. a second switch may be used to caitcel the sequencr of repeating lrvels at any tirnr. Clinically. such a second switch is often prescnbed to permit canceling scanning across an undesired row or scanning down many rows. An added advantage of the cancel switch is when rxtending a selection by scanning. If the end of a scanning selection block coincides with the target then the user could escape and immediately select that block. This eliminates having to scan from lefi-to-right with smaller blocks. Figure 3-7 illustrates typical sequential scanning of the text cunor, cg., down two lines, across three words. and across four characters. There is only one time (Pi + Ki) taken to plan and select the initial movement key. The time between al1 text cursor movements is now only one scan interval (S) except on the first step of a movement Ievel which is delayed (2s). The delay causes the text cursor to pause at the fint character of the next smaller block making it easier to select that block without advancing the text cursor. ,Sequential Repeating Keystrokes / . rsmcd r:ncrdunt xt lzureet GO-zr;- Figure 3-7: Strategy 3: Sequential scanning text keys to move the text cursor. This stratrgy is accomplished transparently by linking sequencrs of repeat loops of keystrokes within individual keys on the on-screen keyboard. Each repeat loop contains one trxt key movemrnt. The par-agr-aph kei*contains a sequencr of paragraphs. lines. words and charactsrs: the liite Lyv contains a sequence of lines. words and characters: the wrd kg*contains a sequence of words and charactrn. The characrer /ce?*contains a single repeat loop of character movements. For example, text cursor scanning beginning at the paragraph level is achirved with the following sequence of repeat loops, Afier moving by pangraphs. i t is necessary to position the text cursor at the beginning of the line with a Error correction must be explicitly designed with this strategy to handle overshooting the target. A number of options are available: limit backward scanning to a single text key increment as in Strategy 2; 0 incorponte backward scaming at al1 levels in a sequence: or incorporate backward scaming at the first level in a scquence. and forward thereafter. Within this thesis. the last option was implemrnted. It assumes that if a mistakr is made. it is by overshooting the targrt at a certain level. Thus. once the user moves behind the target. then scanning will proceed fonvard by the next smaller size. For example. when moving up by lines and after selecting the desired line. the text cursor moves across words from the first charmer of that line. This rnaintains the style of selecting a target in a single scaming operation. The first error correction option was not considered because it is the same as Strategy 2. The second option was considered in a pilot evaluation where it was found to be conhsing to use. 3.1.4.1 Strategy 4: Scanning Text The target insertion point is selected by scanning the text by text groups as if it was an estension of the on-screen keyboard in a single scanning operation. This stratç~ginvolves directly selecting insertion points by scanning the text area rather than moving the text cursor. It is a refinrment of the strategy onginally considered in a prior study (Shein et al. 1990). Paragnphs, lines. words, and characters are highlighted in succession until the targrt insertion point is selçcted. Keys in the on-screen keyboard indicate ai which levrl to start scanning. This approach allows the user to carry over a consistent selection rule from the on-scrern keyboard -to focus on the target point and activate the select switch whenever the target is highlighted. until the target point is selected. Similar to the previous strategy, any point in the text field can be reached with a single scanning operation and attention switching is rninimized. An intent with this strategy was to have the user develop a mental mode1 such that the scanning text was a searnless extension of the on-screen keyboard and that it was unnecessary to think about moving the text cursor. Figure 3-8 illustrates typical text scaming. e.g., down two lines, across three words, and across four characters. Here. there is only one time taken to plan and select the initial text scming (Pi + Ki). The time brtwern al1 scan steps is now only one scan interval (S) except on the first strp of a scanning lrvel which is delayed (7s).This delay causes the highlight to pause on the first srnaller text object giving the user a chance to select it without advancing to the next object. Figure 3-8: Strategy 4: Scanning text to select the insertion point. A similar rationale to that of Strategy 3 exists for the use of a second switch to cancel any sequence of repeating keystrokes. If the end of a scaming selection coincides with the target. then the user could escape from fùrther scanning to select that selection. This eliminates having to scan from lefi-to-right at smaller increments. This strategy is transparently accomplished in a similar manner as Strategy 3 except that it uses krystrokes that normally extend the selection to highlight the text. This involves preceding the text movement key with a In this example. addi tional non-repeating ksystrokes are required between loops to position the staning point. Scanning always Stans at the beginning of paragraphs. lines and words. Afirr selecting a paragraph. Iines are highlighted beginning with the first line of that parapph. Aftrr sslecting a line. words are highlighted begiming with the first word of that line. After selccting a word. characters are highlighted begiming with the first character of that word. Similar to Strategy 3. it was assumed that if a mistake was made. it was by overshooting the target by only a block and a similar error correction stntegy was designsd. Once the user moved backwards by the correct block. scanning staned fonvard by the nezt smaller block at its beginning. For example. whrn moving up by lines and afier selecting the desired line. scaming started by words at the beginning of that line. 3.5 Overdrive Scanning If scanning is applied across GUI objects, such as text, using the natural structure of those objects as scan groupings, the access system has no control over the size of any particular group. This has direct bearing over the time it will take to scan across those objects. In the case of text, for example. a screen of text may only have a few paragraphs and each paragraph may be several lines. Words contain several lerten. However, a line may contain up to 15-20 words which exceeds the ideal number of items in a single scan grouping (Kulikowski, 1982). Thus, it may take a long time to reach a word near the end of a line with those strategies that scan across lines staning with the lefi-most word. This can lead to user hstration and reduce overall productivity. Potential solution lies in adjusting the scan intemal that is the primary factor in determining how long a task takes. A scan interval is designed to be long enough such that the user can respond ro a target being highlighted and activate a switch. When one considers the rationale for setting the scan interval it is suggested that associating a constant scan interval for all steps might be unnecessary or inappropriate. For al1 steps in which the highlight is not over a target. the user has little concern for the scan interval. However, the user does have a concem that there is sufficient time to prrpare (physically and mentally) to be in a position to react when the target is highlighted (Vanderheiden. 1985). Following this line of thought. the time taken to scan to a targrt can br broken down into three periods as illustrated in Figure 3-9. Figure 3-9: Scanning periods: wasted time (A); preparatory time (8);and selection scan intewal (C). The first period (A) consists of scaming over items away from the target: any time spent here is of no interest to the user. The second penod (B) is a preparaiion time positioning onesrlf to respond: this time varies with the physical and cognitive ability of the user and is unrelated to the scan interval. And the third period (C) is when the highlight is over the target; this is the scan interval for which the user has greatest concem and when they must respond. The latter penods (B & C) can be slightly reduced with practice, but any improvements would make littlr difference in overall time taken. The first time period (A) is the only period open to significant irnprovement. However, given that only the user and not the automatic scaming system know the location of the target, the question remains as to how to reduce this time. If the number of steps remains the same, one possibility is to allow the user to shorten the scan interval associated with these steps. A practical implementation of this idea is an overdrive control on the scanning rate. Here. the user intentionally indicates that the scan intcrval be shonrned to move the highlight more quickly across items. Then, the user indicates when the original scan rate should be reinstated to allow sufficient time to prepare to select the target. This method was used in a dedicated communication aid (PMV ~rinter'') in the 1970s as a two- speed linear scanning strategy. One switch was held to scan at a fast rate that drops to a slower ratr when the switch is released. A second switch was used to make a selection. Altemately. with a single switch alone. the scaming started out fast. then switch activation slowed the scanning and a second activation made a selection. It was funher employed in two scanning computçr access systems developed by this author's research team ( Elementary MOD ~e~board".WiViK 2 scan;'). It is not. however. a commonly used strategy. Two methods for overdrive have been designed and programmed into WiViK. One method takes advantage of a second switch with a rimed hold and t-elease action. As long as this second switch is held. the scan interval is shortened by some factor, thus increasing scan rate. When the switch is released. the scan interval retums to its original value. Recognizing that somr users may not be able to perform such an action. another method has been designed to take advantage of a second switch with a discrrtr nctiivtiotz to toggle the original scan rate to a faster ratr. A second activation togglrs the interval back to its original value. L'sing a single switch for overdrive and selection was intentionally not irnplemented because of potential confusion with selection. especially if the scan distance is short. With both WiViK methods the user controls the length of tirne that the overdnve rate is active. A speed factor relative to the scan interval can be set. For example a scan interval of 1 sec. might have a Zx overdrive rate (0.5 sec. scan interval) or a 4x overdrive rate (0.25 sec. scan interval). The faster the overdnve rate, the shoner the time spent in scaming towards the target. Although there is potential for improved user performance, there is no published research data indicating '" .U-Med. Inc.. Forest Park. IL (discontinued) TASH. Inc.. Ajax. ON (discontinued) " Prentke Romich Company. Wooster. OH whether an overdrive control offers any real benefit to the user. Nor are there any guidelines for its use and setting of rates. Overdrive is evaluated here because it can be applied to any of the proposed scaming text stntegies and has the potential to improve productivity. Before any potential can be realizrd. however. it is important to first understand the limitations and usability aspects of overdrive. With Strategy 2. overdnve might reduce planning time and effort that might othenvise be takrn derermining stntegic text jumps by supplementing simple scanning by texi steps which ordinarily leads to wasted scanning time. With Strategies 3 and 1. overdrive might be employed to reduce wasted time when scanning across a large group. such as many words in a line. 3.6 Impact of Subject Factors on Text Scanning Strategies The use of able-bodied subjects in the evaluation of the proposed text scanning strategies and overdnve scanning offers a practical means of accessing a sufficiently large pool of subjects with homogeneous physical skills in order to identiQ the salient features of each strategy. Through the use of scaming with the samc type of switches that users with disabilities might use. able-bodied subjects simulate conditions of physical disability. Since single-switch sca~ingplaces certain operating constraints on the user regardless of any disability. performance by an able-bodied prrson may be viewed as expert performance to which a user with a disability may approach but not likely exceed. The issue of concem in evaluating the strategies is not how a person can intenct with a switch. but rather the effectiveness of particular scanning strategies given a fixrd switch arrangement and fixed user motor capabilities. It is suggestrd that the key difference between able-bodied subjects and usen with disabilities is that able-bodied subjects are not likely to make incorrect switch activations due to impaired or reflexive movements. Individuals with physical disabilities ofien exhibit muscle spasticity. weakness, or abnomal reflex patterns that result in inconsistent use of a switch. However. these impairments are highly individualized and would impact al1 scaming methods. Since users with disabilities may make errors of switch activation at any given time, the number of switch activations that a particular technique requires for both standard selection and for enor correction will be an important factor in evaluating the techniques. It is to be expected that any errors of switch activation would be due to confusion or mental errors induced by the usage of a particular strategy since there would be no physical reason for an srror. Such errors should be consistent within other individuals and would be additive to the 'naturally occuning' mors made by a person with a disability. Nrvenhelrss. it is recognized that the participation of able-bodied subjects reduces the generalization of results to any specific population of people with disabilities. 3.7 Summary In this chapter. the notion of task transparency is explained and expanded upon through the dclineation of specific strategies that apply the concept of scanning within the tcxt area of an application. These offer potential improved performance over the standard keystro ke strategy that moves the text cursor by one step for evrry key chosen in the on-screen kryboard. Thrsr stntegies are controlled directly by an on-scrren keyboard, WiViK. which has been customized for sach strategy. WiViK provides the means to use the keyboard channel as a transparent information carrier of user control. Tlir scanning text keys strategy takes the viewpoint that the primary user task involves moving the text cursor. It uses repeating text keys to engage the text cursor in scaming across text objects. The sequential scanning text keys strategy takes a similar viewpoint of moving the text cursor. However, it links text keys such that the user can scan to a target point in a single operation through a sequence fkom large to small groups (paragraphs, lines, words, characters). Rather than move the text cursor. the text scanning strategy allows the user to select the insertion point by scanning across the text in diminishing text sizes (paragraph, line. word, character). This allows the user to focus on the on the target location and activate the select switch whenever it is highlighted. Overdrive scanning, is discussrd as a method to enhance to the user's productivity with the trxt scanning strategies. This approach addresses the issue that time spent scanning across many items. such as words in a sentence. ahead of the target is 'wasted.' Overdrive sca~ingemploys a second switch under user control to scan more quickly across an array of items. Two overdrive methods are described. One method requires a holding action and the other rnethod requires two discrete switch actions to toggle the overdrive. Thesr scaming strategies lead to a number of questions conceming usability and user demands which must be ascertained in order to best design altemate access systems that incorponte task transparent scanning. Subsequent chapters describe the cvaluation of thesr stntegirs. 4 Development of Evaluation Tools 4.1 Introduction This chapter descnbes the development of the predictive and rxperimental tools that were used to evaluate the srrategies proposed in the previous chapter. Analytic computations to predict performance are descnbed for the four insertion point selection strategies with respect to the total number of on-screen keys required, switch activations. and total tims. Two software test applications are then descnbed. The first was used to rvaluate thoss four strategies. The second was used to cvaluate overdrive scaming. Vanderheidcn ( 1985) demonstrated that user performance with scanning strategies could bs predictrd by analyzinj the scanning strps with respect to a represeniarive sample of tasks. 1 have used thoss concepts to devrlop my own prediction computations sprcific to the proposed strategies. These predictions provide estimates of error-free performances. They are also useful to identiS, potential usability issues. The predictions require. however. some knowledge of specific user actions, since it is the user who chooses how to move through the text. The nlimber of choices for actions vanes with srrategy. Stratrgies I and 2 have the geatest number of alternative pathways to move the text cursor to the desired insertion point. A visual examination of the tasks is required to determine the possible actions and the number of steps. This examination must follow some rule-base for consistency. On the other hand. Strategies 3 and 4 can both accomplish the task in a single unique scanning operation and their ideal performance can be calculated using the text distance between the starting and target points. Expenmental data fiorn human subjects was needed to provide realistic estimates of user- detennined planning and rxecution times to apply in the predictions. More importantly. experimental data was needed to gain a greater understanding of the mechanisms by which users would react. adapt. and strategically empioy each of the strategies. and to highlight potential mors thar mipht anse. Test software applications were developed specifically to gather such information. Custom applications were used instead of a conventional word processor so that the presenration of the tasks could bc controlled and to collect objective data. Al1 of the strategies. however. were transparent to a word processor. 4.2 Prediction of Error-Free User Performance 4.2.1 On-Screen Keyboard Key Selections With Strategies 1 and 2. there are many possible ways to move the insertion point to a target location. These. however. are very individualistic and Vary with the spatial and problem-solving skills of the user. Therefore. a consistent approach to choosing movement keys from the on- screen keyboard is required to uniquely predict performance. It is then possible to calculate the number of moves rrquired to move to the beginning of a selection starting from a known point (reg..the upper lefi-hand corner) based upon the target location (pangraph. line. word. charactsr). Prrforming a similar calculation on the end of a selection for Strategy 1 and Strategy 2 is more difficult because the word lengh varies in each line. Therefore. predicted movemrnts must be done by manual examination of each target selrction for those scaming strategies. A conservative rule to predict movement steps, and thus required key selections, is to consider only character. word. line and paragraph keys begiming with large movements followed by smaller moves as the target is approached. This is conservative because it does not involve srnarter moves that might achieve greater movement in fewer steps. An exhaustive approach would require the sampling of actual expert user performance to detemine ideal movement sequences. Such expert movements may include Strategy 1 uses as many keys as necessary to individually step the text cursor from its starting point to the target insertion point: -:y= P+L+W+C Strategy 2 should use the same keys as Strategy 1. but should only require one of each differrnt key. because of its repeating function. With Strategy 2 it is possible. but not likely done. that any point may be reached with a single repeating charactrr movement (e.~..charactrr). It is likel y that the user can reach the target insertion point in ihree or four moves: Strategies 3 and 4 only require one key (ideally) to set the insertion point: 4.2.2 Select Switch Activations Calculation of the number of switch activations follows directly from the number of keys and the movement steps made in the text area. The following equations for the total number of switch activations for each of the strategies are based on knowledge of the conservative rule. Let SwitchActs = number of switch activations P = numbrr of para_gaphs ahead L = number of lines ahead in targst paragraph W = number of words ahead in target line C = number of characters ahead in target word Strategy 1 requires a constant two select switch activations to select each movement key from the on-screen keyboard. Thus, the total number of activations required to reach the target cquals twice the total number of movement (sirnilu and dissimilar) steps made. Strategy 2 requirrs two switch activations to select each movement key fi-om the on-screen keyboard. An additional activation is required when that movement key repeats to stop it. Thus. the total numbrr of switch activations required to reach the target equals three times the total number of keys. Strategies 3 and 1 require two activations to select the one movernent kry fkom the on-screen keyboard and one, two. three. or four additional activations to stop character, word, line or paragrap h scanning respective1y. Min = 3: Mar = 6 With Strategy 1. al1 of the time is spent scaming the on-screen keyboard. With the other strategies. some time is spent scanning the on-screen keyboard. and the remainder is spent scaming the text area. In calculating the rime within the on-screen keyboard. the panicular arrangement of keys must be known. From this arrangement. the nurnber of scaming steps to reach each key can be calcuiated. Figure 4-1 illustrates the arrangement of keys and associated scanning steps used experimentally. Here it is assumed that there is a doubling of the scan intemal as a delay on the first row. and a similar delay on the first item within a row. It is also assumed that the user will select a key on average. mid-way through a scan interval. Thus. the Right Right Word Down Line Down Para Scan Intervals: 2 Scan Intervals: 3.5 Scan Intervals: 4.5 Scan Intervals: 5.5 I Left 1 Left Word 1 Up Line 1 Up Para 1 Scan Intervals: 3.5 1 Scan Intervals: 5 1 Scan Intervals: 6 1 Scan Intervals: 7 I End 1 Home 1 Page Down 1 Scan Intervals: 4.5 1 Scan Intervals: 6 ( Scan Intervals: 7 1 Scan Intervals: 8 Scan Intervals: 5.5 1 I Figure 4-1 : Predicted scanning intervals per movement key in the on-screen keyboard (see Figure 3-4). Equations for predicting the total task time given the identification of a movement sequence to a target and the above on-screen keyboard assumptions. are provided in the next four sub-sections. .411 equations assume error-free performance in which any planning is achieved within the first scan period. This is similar to keystroke model calculations suggested by Card, Moran and Newell ( 1985) but micro elements of cognitive processing are not considered because they are contained within a larger scan interval. 4.2.3.1 Strategy 1 : Standard Keystrokes With Strategy 1, the total time is the surn of al1 individual times spent scanning the on-screen keyboard to select the keys needed to move the text cunor to the desired insertion point. Let K = on-screen keyboard scan intervals to select the im movement key S = overall scan intemal Equntion 4.2.3.1 4.2.3.2 Strategy 2: Scanning Text Keys Witb Strategy 2, the total time is the sum of individual times spent scanning the on-screen keyboard to select different size movement keys plus the time spent repeating each movement key. unless the key is non-repeating. As in the on-screen keyboard there is a delay equal to one scan interval on the tirst repeated movement and it is assumed that the movement is stopped mid-way through an interval. Let K= on-screen keyboard scan intervals to select the i" movement key S = overall scan interval T= text scanning intervals Equation 4.2.3.2 4.2.3.3 Strategy 3: Sequential Scanning Text Keys With Strategy 3, one portion of the total tirne is spent selecting a single movement key. The remaining portion of time is spent with scanning movements within the text area. This time is a surn of scan intervals associated with evev movement step. As with the on-screen keyboard there is a delay equal to one scan interval on the first repeated movement within a group. and it is assumed that the movement is stopped mid-way through a step. For example. if the target was one paragraph distant. it wouid be sdected in one-half of a doubled scan intervat or one intewal. If. for rxamplr. the target was three paragraphs distant. it would be selected after two scan intervals on the first paragraph plus one scan interval on the second paragaph plus one-half scan interval on the third paragraph for a total of 3 '/r scan intemals (P + 0.5). Let K~.~.~.~= number of scan intervals within on-screen keyboard for down paragraph. down linr. right word. and nght character respectively P = number of paragraphs ahead f L = line position in target paragraph (plus 1 if highlighting) if P >O. else number of lines ahead W = word position in target line if L> O. else number of words ahead f C = charactrr position in target word (plus 1 if highlighting) if W>O. elsr number of c haractsrs ahead S = overall scan interval Equation 4.2.3.3 f Adjustment for extended highlight ending in last line of a paragraph and before the first character of a word Yole: "n" refers to "AND" in above equation. 3.2.3.4 Strategy 3: Scanning Teat Time calculations with Strategy 4 are identical to that of Strategy 3 with the exception of some variations in the number of text scanning steps described below. Let KP.L.\v.C= number of scan intervals within on-scrcen keyboard for down para_gaph. down linr. nght word, and nght character respectively P = number of paragraphs ahead ph1 L = Linr position in target paragraph if P >O. else number of lines ahead phrs 1 W = word position in target line if L> O. else number of words aheadplrrs I C = character position in target word (plus 1 if highlighting) if W>O. else number of chancters ahead plus 1 S = overall scan interval 4.3 Text Selection Test Application A simplified psçudo-tcxt application was designed and programmed using Microsofi Visual ~asic"under Microsofi Windows 3.1 ruming on an IBM microcornputer. The elements of a text editor were abstracted to eliminate the readingisearching of the text so that subjects could strictly focus upon the selrction task independent of ihe idiosyncrasies of a word processor and its displayed type. '' Microsoft Corporation. Redmond. WA The test application displayrd a window with variable numbers of rows and columns as illustmted below in Figure 4-2. Within this experiment, a dimension of 60 columns by 20 rows was used. This was representative of a typical screen view of text in a word processor. Instead of leners, small gray boxes. similar to 'greeked' text in publishing software. were displayed in groupings to fom nndom sized blocks (sirnilar to words). An average length for these blocks was adjustable. Lines were filled with these blocks with one space between blocks. ParaWphs of pseudo-random numbers of lines were generated. Figure 4-2: Experimental test application. Two target grid locations were coloured at random locations for each trial. A green grid location indicated the starting point to begin highlighting a block of data: a red grid location indicated the ending point of the block. The task was to first set the insertion point at the green grid location, select the extend mode, move to the red grid location, and turn off the extend mode. The text cursor moved with standard keystroke equivalents as defined within a common word processing application. Microsofi ~ord".Rather than a vertical line or 1-beam text cursor, a single grid location was highlighted similar to an overwrite box cursor. This ensured that the scanning text cursor was highly visible within the experiment. It is recognized that this may bias " Microsoft Corporation. Redmond. WA the results associated with the techniques that move a text cursor because it would be more visible. In the extend mode. there was no difference sincr a block was highlishted. A set of 25 random pattems of text blocks and targets was generated when the test program was initiated. These are illustnted in Appendix B. These patterns were representative of potential editing tasks that might be faced in an actual word processor. The lengrh of the block varied and some tasks were easier to accomplish than others. Twelvr pattems had the end point below and to the left of the begiming point. and thineen pattems had the end point below and to the right. Al1 subjects used the same pattems and targets but the order of presentation was randomized. Each scanning strategy used a common on-screen keyboard arrangement and definitions (Appendix A) as described in the previous chapter. The subject selects the 'Stan' item within the on-screen keyboard to initiate the test. The screen arrangement of the test application and WiViK as it was used in the experiment is shown in Figure 4-3. Figure 4-3: Screen arrangement of test application and WiViK on-screen keyboard showing partial completion of a block selection. The following data were autornatically collected by the test application during each trial: test block pattern number: time to complete each trial: number of activations of the select and cancel switchrs: count of each on-screen key selected: and history of on-screen keys selected. The time to complete each trial was calculated fiom the initial selection of the 'Stan' key and rnding with the 'Stop Extend' key after successfÙlly highlighting the targer block. A 'background task' program (a Dynarnic Link Library) was pro_mmmed to automatically count switch activations. Switch counts for both switches were initialized after selecting the 'Start' key. Final switch counts were recorded at the end of the trial. These data were saved in a comma-delimited text tile format (.CSV) for later analysis. 4.4 Overdrive Test System Another software test program was designed and programmed to specifically test and measure performance selecting a single target in an array of 15 items using overdrive (Figure 4-4) with simple item sca~ing.This target array is anaiogous to a single line of text with a typical number of words. Rather than use text. simple graphic boxes were used as items. This reduced distraction and allowed the subjects to focus on the task at hand. I H Elle Çustomizc Seka Aâditrons H~OIl Figure 4-4: Screen image of test application for overdrive scanning. A target was displayed as a solid green box within one of the 15 item boxes. Boxes were hishlighted by inversion (from white to black) as they were scanned. This highlight moved lefi- to-iight across the amy whenever a nght arrow key was entered. To achieve scaming of the target array. WiViK was used again. A single key was programmed to be displayed in WiViK to repeatedly enter the The software was programmed to run sets of 30 trials with each item targetrd twicr. Targets wsre randomly displayed. The test software automatically tracked time that the highlight spent on each item as well as the target and selrcted item. This data was saved in a file for analysis. 4.5 Summary Predictive and experirnental tools were drveloped to rvaluate the stnteçies proposed in the previous chapter. The total number of on-screen keys required. switch activations. and time can be calculated to predici error-free user performance for each stntegy to select the insertion point as pan of a text selection task. These calculations are based on a known number of steps that the user must make, specific keys that would be chosen. anticipated switch activations. and a fixed scan interval. Thrse may differ From actual use. Thus. experimental tools were designed and developed to capture actual usage information. Two software test applications were developed. The first application presents randomized text selection tasks and records performance data. This is a generalized application that works with any access strategy that manipulates the text cursor. The second application presents target items within a single-line array that can be selected through item scaming. It provides a base to evaluate overdrive scaming. Along with both applications. WiViK on-screen keyboard has been customized and used as the access system. These tools are applied in evaluations described in the next two chapters. Evaluation of Text Selection Strategies 5.1 Introduction This chapter drscnbes and discusses the evaluation of the proposed tsxt scanning strategirs described in Section 3.44 applied to a representative set of text selection tasks. Two types of evaluations wrre performed. Fint. the strategies were evaluated using a predictivr analysis of user performance using the computational modrls denved in the previous chapter. This provided an estimation of error-free performances. initially with consemative predictions of user actions. Second. an rxperimrnt was conducted with human subjects to gain additional knowledge of user strategies. short-tenn Ieaming, errors. and perceptions that were not predicted. Experimental data were also needed to effectively compare Strategies 3 and 4 with Strategies 1 and 2 that utilized several user-controllrd steps. The brst user strategirs were then identified for Stntegies 1 and 2 to predict expert performance. Through these evaluations, advantages and disadvantares of each stratrgy were idrntifird and design guidelines were drrived (see Chapter 7). 5.2 Prediction Methodology Error-free performance data of the subjects with each scanning strategy were predicted as detailed in Section 4.2 (Prediction of Error-Free User Performance). Calculations were performed on a representative set of 25 selection tasks (Appendix B) which were also used in the experimental trials. Eac h task consisted of identiwing the staning point of the selection, choosing the extend selection key. identifjring the end point of the selection, and choosing the stop extend selection key to end the task. Thus, the data consisted of a summation of computations for these four sub-tasks. Specific predicted keys and movement steps for each of the 25 trial patterns are provided in Appendix C. With Strategies 1 and 2. a conservative approach to moving the text cursor was initially followed and expected movements were determined by manual examination of each trial pattern brcause a priori knowledge of user movement tactics was required. This conservative approach did not consider jumping across the text with the No reversing of direction was considered. except when the end point was to the lefi of the begiming point. In reaching the end target point, CDown Line> movements maintainrd the horizontal position in a line. allowing leftward movements to reach the end point. The following movement keys were considered: Prrdicting movsments was more straightforward with Strategies 3 and 1. The lar,*est movsment key ( Time calculations were based on a number of assumptions. The number of scanning steps to select an individual key within the on-screen keyboard layout was constant as shown in Section 4.2.3 (Figure 4- 1 ). Thrse suggested scaming steps assumed a doubling delay factor on the first row and first key in a seiected row. It was also assumed that the user would select a key at the mid-point of a scan interval, including the lengthened interval of the fint row and column. The same scan interval used within the expenmental trials (1 sec.) was used in al1 calculations. 5.3 Experimental Methodology 5.3.1 Goal The goal of this experiment was to explore and compare the use of each proposrd scanning strategy to select text within a representative set of tasks using data from actual use. In particular. performance gains in the text scanning Strategies 2, 3 and 4 with respect to standard krystrokes were expected by reducing: on-screen keyboard selections and related attention shifis: time to complete selection tasks: number of switch activations: and overall task timcs. It was also expected that each sca~ingstrategy would have particular tactics for reaching the target as well as unique styles of errors. It is recopized that individual motor, cognitive. and visual-perceptual abilities and their limitations due to disability. may have as much influence on the rffectiveness of any scanning strateçy as its optimally used merits or disadvantages. 5.3.2 Pilot Experiment Prior to canying out the full experiment described here, the protocol was piloted to evaluate the test system and to identie clear deficiencies with each proposed scanning mrthod. Four groups of four subjrcts rach panicipated. They performed one introductory session and one trial session. The outcome of this pilot included the following: revisions to the test application to correct progamming deficiencies which lead to inconsistent movements related to certain keystroke equivalsnts: correction of software bugs leading to application errors: improvemrnts to the data collection: improvrments to the subject instructions (especially for Strategies 2 and 3 ); and improvements to the WiViK keyboard definitions. One scaming strategy change related to the error correction strategy employed with Strategies 3 and 4. In the pilot experiment the cursor scanned backward through a11 levels when a backward movement key was chosen. This was found to be extremely difficult to use. Instead, the method described in Section 3.4.4.3 were designed whereby the fint level chosen (e-g., paragraph) was scanned backward, then subsequent levels were fonvard. This allowed al1 final selections to be made through foward scanning that proved to be an easier task. 5.3.3 Experimental Design The experiment consisted of repeated trials using the test application descnbed in the previous chapter (Section 1.3 Text Selection Test Application) to select blocks of 'text.' There were four groups with five subjects in each group (twenty subjects in total). A between-subjects design was employed to eliminate ordering effects of scanning strategy as a factor because preliminary trials indicated that there was asymmetric carryover between strategies. When moving between scanning strategies. confusion could arise concerning which strategy was operating since the on- scrrrn keyboard was visually the same and feedback in the test application was similar. Confusion could Iead to erron related to expected cursor movements. Thus, rach group was assigned to one of the four scanning strategies: Strategy 1 : Standard Keystrokes: Strategy 2: Scanning Text Krys: Strategy 3: Srquential Scaming Text Kcys: and Strategy 3: Scanning Text. Subjects were nndomly assigned to each group. Al1 groups used an identical rowkolumn scanning technique to select items from the on-screen keyboard. Subjects participated in one introductory end five repeated experimental sessions of 25 trials èach. The task in each trial was to select a 'text' block. Dunng the introductory session. subjects wrre first positionrd appropriately. They then rrceived a consistent explanation of the access method and the use of swirches to makr selcctions through scaming and to move the cursor across the 'text' (Appendix D). The researcher lrd the subjects through the completion of sample tasks. They were then allowed to practice through one complete set of 25 trials. Each experimental trial session began with the researcher positioning al1 components and rnsuring that the subject was comfortable. Subjects were provided with a brief practice period ( 10 sample trials) followed by the 25 experimental trials. Each trial began with the subject selecting the 'Start' kcy on the on-screen keyboard. Upon successful completion of a selection, the trial automatically stopped. the next trial was prepared, and the system paused waiting for the subject to select 'Start' again. Each session took approximately 15 minutes to complete. 4 row/colurnn sca~ingstrategy was used to select items within the on-screen keyboard. In actual use, the scaming interval would be optimized to match the abilities of the user. In this experiment, a fixed scaming interval of one second was used to permit cornparisons across individual subjects. An additional delay of one second was applied to the first row scanned. the first item within a row. and the fint item of a reprating movement or movement group. Data collected dunng the session were saved afier the last trial. During the trials. the researchsr only intervened if there was a physical problem (such as a switch not properl y activating) or if the subject becarne contiised with the methodology. Any trials in which such an intervention was made were repeated. Following the completion of each session. subjrcts were querird by the researcher using open-ended questions (Appendix D) to elicit information related to persona1 impressions: ease of use; speci fic likes and dislikes; movement strategies: points of frustration: degree of control: and satisfaction. 5.3.4 Physical Arrangement Al1 testing software ran on an IBM persona1 computer with a standard 11 in. VGA display placed directly in front of the subject (Figure 5-1). Subjrcts sat on an adjustable office chair. Common human factor guidelines for VDT operators were used to position the monitor hright. vicwing distance. and chair height and back support to accommodate individual differences betwern subjects. The input device was fi'red for a11 subjects: two pad switches positionrd on the drsk surface directly in front of the user. Thess switches were activated by the user's dominant band. Figure 5-1 : Physical arrangement of computer monitor, switches and subject. The twenty subjects were able-bodied with no motor. cognitive or visual-perceptual dçficits that would interfere with the tasks. Staff mernbers at the researcher's institution participated. The subjects were asked to sign an informed consent form afier reading an information shect. AI1 subjects had intermediate experience editing text in a GUI. They understood the concepts of moving the text cursor with arrow keys. selecting text. cutting, copying, pasting, and simple character formatting (fonts, sizes, and styles). It was recognized that there were some individual variations in the sub-skills associated with these tasks. None had pnor experience using any of the scanning access rnethods. Pnor to any trials, the subjects were informed of the requirrments of the trials and asked to sign an infonned consent form after reading an infornation shret. The hypotheses and any preferences of the researcher were not disclosed. 5.3.6 Data Analysis Data from the fint session was discarded brcause the subjects reported that they wsre still leaming the test application task as well as the scaming strategies. This session was thrrefore considered an additional training session. Data was then organized as follows. To ascertain learning effects. sessions 2 and 3 were grouped together as Session Group 1 and sessions 4 and 5 wcrc gouped together as Session Group 2. The total number of key selrctions. total select and cancel switch activations, and total time were first rxamined by organizinp and averaging the data across 5 subjects per strategy, by 4 scan strategies, 2 session groups. and 25 trial patterns. Summanes of the observed data are provided in Appendix E. This data was analyzed using an Analysis of Variance (ANOVA). Cornrnents made by the subjects were reported anecdotally and are incorporated into the results of this chapter. A second level of analysis was done to examine more specific variables of interest including usage of individual movement keys, rnovement strategies, and under and overshooting the target with Strategies 3 and 4. In this analysis. the data was further subdivided to include the begiming and end points. Summanes of al1 statistical analyses are provided in Appendix F. A Student-Newman-Ksuls (SNK) test (which controls the type 1 experimentwise error rate under the complete null hypothesis but not under partial null hypotheses) was used to identi- specific differences between variables. The SNK test was chosen as being appropriate for this exploratory exprrimental design. Bonferroni or Scheffe's multiple cornpanson tests were not used because these tests are more conservative in rejecting the nu11 hypotheses and are more frequently used in confirmatory rxperimcnts. This experiment was considered exploratory because it was the fint gathering of data with the proposed strategies. In order ro examine how subjects may employ the scan strategies. they were given freedom of how to use each strategy. Thus. the specific utilization of strategies was explicitly not tightly controlled. Observed data were compared with predicted performance scores by calculating a t-statistic on the average difference in scores across the 25 trial patterns for each strategy. This t-statistic was used to test the hypothrsis that the di fference was zero. 5.4 Results 5.4.1 On-Screen Key Selections The predictrd and observed number of keys are shown in Table 5-1 as averages in scan strategies across the 25 trial patterns and both session groups. An ANOVA on the observed number of keys indicated a significant differrnce (F(3.28)=568.15: Pc0.000 1 ) among the strategies and an SNK analysis indicated that Strategy 1 used significantly more keys than the others. Strategy 2 usrd significantly fewer keys than Strategy 1 but more than the others. Strategies 3 and 1 used the fewest number of keys and were equivalent. Variation between trials was small with thrse latter two strategies. Al1 strategies used the 'extend' and 'stop extend' selection keys identically. The ANOVA indicated no significant difference (F4) between sessions. There was a significant difference (F(24,28)=4.12: Pc0.0001) between trial patterns indicating a range of task dificulty. 1 Strategy 1 Strategy 2 Strategy 3 Strategy 4 Pred. Obsew. Pred. Observ. Pred. Observ. Pred. Obsew. Right 2.7 2.6 0.8 0.9 0.1 0.1 Right Word 5.6 3.0 1 .O 1.O 0.04 O. 1 0.04 O. 1 Down 3.4 2.2 1.5 1.2 0.44 0.5 0.44 0.6 Down Para 2.7 2.7 1.5 1.4 1-52 1.5 1.52 1.4 Left 2.0 0.9 0.6 0.5 - 0.2 O. 1 Left Word 1.3 1.3 0.5 0.4 0.2 0.1 UP 0.7 0.3 O. 1 O. 1 Up Para 0.1 End 0.3 0.2 O. 1 Home 0.2 0.1 ExtendJStop 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 TOTAL Keys 119.6 I2.5)16.2 I1.41 7.9 t 0.6 1 8.0 k 0.5 1 4.0 1 4.9 t 0.2 1 4.0 1 4.4 2 0.1 1 Table 5-1 : Average predicted and obsewed rnovement keys selected for each scanning strategy (k 95% confidence interval) per trial. Strategy 1 used approximatel y 3 -4 fewer keys on average than conservatively predicted (t=-3 -64. P Generally. subjects using Strategy 1 moved to the target by first choosing larger rnovements than smaller movements. When the target was in the second half of a line, they jumped to the end of the line followed by backward movements. Similarly, if the target was near the end of a paragraph, subjects often jurnped to the end of the paragraph before moving backwards. Subjects reported that they found text cursor movement fi-ustrating and tiresome. especially when repeated movements were required because an individual key only moved the text cursor by one step. They preferred to minimize repeat selections even if keys used in jumping took more scan steps in the on-screen keyboard. Occasionally. subjects took advantage of large words in one line to jump fàrther before moving to the next line if they noticrd smaller words in the next linr requiring more movements to cross. There was no significant difference between the average number of selec ted keys with Strategy 2 and the keys conservatively predicted (t=O.jO. PC0.62). However. the specitic key usage was different. The subjects generally followed similar movement sequences to those in Stntegy 1. but used fewer strategic moves as indicated by a slight reduction in the use of cUp>. Both Strategies 1 and 2 had an advantage when extending selections from the middle of one line to the middle of another line. because the subjects did not have to movr across fiom the lefi-hand margin as was the case with Strategies 3 and 4. Subjects used backward movemrnts at the word and character level if the target point was to the lefi of the starting point. Backward movsmcnts were also used dong with upward Iine movement after intentionally overshooting the target with a paragraph step. if the target was near the end of a paragraph. Of panicular interest with Strategies I and 2 were the number of different movement sequencrs (cg.. With both Strategies 3 and 1 the average number of selected keys obsewed was consistently higher (t=9.69; t= 1 0.30, P<0.00 1 ) than predicted. The presence of ~RightCharacter>. 5.4.2 Select Switch Activations The predicted and observed average number of select switch activations are shown in Table 5-3 as averages in scan strategies across the 25 trial patterns and both session groups. Strategy 1 Strategy 2 Strategy 3 Strategy 4 Predicted 39.3 k 5.0 21.8 I1.7 15.5 I0.3 15.5 i 0.3 Table 5-3: Average number of predicted and observed select switch activations (I%Oh confidence interval) to comptete the experimental tasks per scanning strategy and session group. An ANOVA of the observed switch activations data indicated a significant difference (F(3,28)=30?.41 : P<0.0001)among the scan strategies and an SNK analysis indicated that Strategy 1 had significantly more select switch activations than the other methods. Strategy 2 had significantly fewer activations than the standard Strategy 1 but more than the others. Strategies 3 and 4 had the fewest activations and were equivalent. The ANOVA indicated no significant difference (F< 1 ) between the sessions. The select switch usage did not Vary significantly across sessions. As before, there was a significant difference (F(24,28)=6.85: P<0.000 1 ) among the trial patterns. On average. Strategy 1 accomplished the tasks with 5.8 fewer select switch activations (t= -3.1 ; Pc0.005) than consrrvatively predicted. There was no differencr betwçen the observed and rxpected activations with Strategy 2 (t=0.9: NS). Strategy 3 used 1 .Z more activations expectrd (t=M P By re-applying the cquations and niles for predicting performance for Strategies 1 and Z based on the optimal key sequences most ofien chosen by the subjects. an average of 17.7 switch activations is predicted for Strategy 1 and 18.8 for Strategy 2. 5.4.3 Cancel Switch Activations Ovenll. the average number of times that the cancel switch was used was relatively srna11 with no significant differencçs (Fcl ) ansing from an ANOVA on the observed data. Funher analysis was warnnted using a proportion of cancel switch activations to the total number of switch activations because previous anal ysis drmonstrated a signi ficant di fference between total select switch activations. These proportion da ta were first subjected to an arcsine transformation ( Snedecor & Cochran. 1967) to account for non-normal distribution of proponional data. A subsequent ANOVA then indicated a significant difference between strategies (F(3.28)=85.78; PcO.0 140) and an SNK analysis showed that subjects using Strategy 3 employed the cancel switch proponionally more fiequently (0.06) with respect to the total switch activations than the others. There was a small Ieaming effect with the first session group having greater proponional cancel switch usage (Fi 1,28)=5.13; Pc0.0248). Subjects using Strategies 1 and 2 employed the cancel switch to restart scanning in the on-screen keyboard if they missed the row containing their desired key, or if they selected the incorrect row. In addition to those situations, subjects using Strategy 3 sometimes employed the cancel switch to stop the trxt scaming in the following three situations. The first situation was when they were confused as to the scanning level (e-g.,scanning by paragraph, line or word) when stepping doum two Irvels at one time (e.g., when the target was in the first line of a paragaph. or first word of a line). The second was to quickly escape from text scanning without having to repeatedly activate the select switch. The third was when the desired selection was highlighted before stepping down to the final character level. Subjects using Strategy 4 did not learn to use the cancel switch as effectively for these latter situations. because activating the cancel switch lefi a highlighted block within the text area. The staning point for begiming the nrxt block scaming was then unclear. 5.4.4 Task Tirne The predicted and observrd average number of overall times (seconds) to complrtr the selection tasks are show in Table 5-4 as averages in scan strategies and session groups across the 25 trial patterns. An ANOVA of the observed time data indicated a significant difference (F(3.3 1 )=8 1.43: P<0.000 1 ) among the scan strategies and an SNK analysis indicated that Strategy 1 was significantly slower than the other methods. Strategy 1 was significantly faster than Strategy 1 but slower than the others. Stntegies 2 and 3 were the fastesr and were rquivalcnt. The ANOVA indicated a significant difference (F( 1.3 1 )= 19.10: P<0.000 1 ) betwren the session groups where the total time decreased from the first session group to the second suggesting sorne leaming effect. There was no siçnificant interaction between strategy and session group (Fe1 ). As anticipated, the total times significantly varied between trial patterns (F(21.3 1 )=2 1.48; P<0.000 1 ) indicating a range of difficulty between trial pattems. ------Strategy 1 Strategy 2 Strategy 3 Strategy 4 Predicted 78.6 + 9.2 54.9 i 4.5 48.6 I2.3 50.1 k 2.3 Session Group 1 71.1 + 5.9 55.5 i 4.4 54.6 + 3.1 61.5 2 2.9 Session Group 2 67.0 + 5.8 53.4 14.2 52.2 i 2.8 56.2 i 2.5 Observed Avg. 69.1 t 5.8 54.4 I 4.2 53.4 * 2.9 58.8 * 2.5 Table 5-4: Average time (seconds) (295% confidence interval) to complete the experimental tasks per scanning strategy and session group. Subjects using Stratem I accomplished the tasks 9.6 sec. faster on average (t=-3.64. P (t=-0.3 1. Pe0.76). Strategy 3 was 4.8 sec. slower (t=8.1. P<0.000 1 ) and Strategy 4 was 5.7 sec. slower ( t= 14.2. P<0.000 1 ) than predicted. Subjects reported feeling stressed using Strategy 1 within the scanning delay on the first row of the keyboard. During this delay. they had to shifi attention to the text and determine the outcome of their Iast movement. detemiine the distance yet to move. plan their action. and shifi back to the keyboard to locatr the target key and follow the scanning ro make their selection. When subjects were unable to complete the planning in time. scanning continued and wrapped around the rows adding to overall time. With Strategy 2. subjects took advantage of the time when the text was being scanned to plan the next movr to be ready to make a selection. This reducrd stress and unwantrd scanning wnparounds in the on-screen keyboard. By re-applying the equations and rules for predicting performance for Strategies 1 and 2 based on the optimal kry sequcncrs most ofien chosen by the subjects. a reduced average time of 58.5 sec. can be predicted for Strategy 1 and 45.1 sec. for Strategy 2. Subjects using Strategy 2 reported some lost tirne rrsulting frorn confusion between repeatinç and non-repeatinç keys in the on- screen keyboard. If they confused a non-repeating key (e-g., Longer than predicted times with Strategies 3 and 4 were due to errors. When the subjects ovenhot the target point they tended to travel several steps past the target as they stepped down through subsequent levrls with the select switch. Correction took longer because there were more steps to travel. Strategy 3 users were more likely to use the cancel switch in this situation and hence did not overshoot as far as those using Strategy 4. The additional overshooting with Strategy 1 accounts for its slower time. Subjects using Strategies 3 and 4 suzgested that some time might be gained by reamnging the iayout of the on-screen keyboard because the paragraph and dom keys were used the most frequently. The impact on overall time for al1 strategies through the rearrangemsnt of keys is çxplored in the next section. 5.4.5 Potential Time lmprovements Through Keyboard Re-Layout Re-amnging the keys such that frequently used keys be accrssed with fewer scan intervals can reduce time. As an illustration of this. alternative Iayouts are presented in the following subsections that arrange the keys according to the fiequency of use for each of the scanning stratrgies. using the proportional distribution of key usage per scan strategy showvn in Figure 5-2. This is based on the optimal key usage observed with Strategies 1 and Z and crror-free usage of Strategies 3 and 3. Proportion of WiViK Keys Used WNiK Key Figure 5-2: Relative proportional distribution of key usage with respect to the total number of keys selected per scan strategy Total times to perforrn each of the 25 trial patterns were calculated using the equations given in Section 3.5 assuming error-fiee performance. Appendix G details the average times for each trial pattern for each of the strategies before and afier the on-screen keyboard rearrangement. Optimal rnovement sequences for Strategies 1 and 2 were uscd. The computations demonstrate that al1 of the strategies benrfit by arranging the on-screen keyboard according to frequency-of-use. but Strategies 3 and 4 benefit the most since fewer on-screen keys need to be availablr. 5.4.5.1 Strategy 1 : Standard Keystrokes An average total time of 53.8 sec. cm be calculated for the re-amnged layout shown below versus 58.5 sec. for the standard layout. for a saving of 846. - -- Down Para Right Down Line Left Intervals: 2 Intervals: 3.5 Intervals: 4.5 Intervals: 5.5 Selections: 2.7 Selections: 2.0 Selections: 1.8 Selections: 0.7 Right Word Left Word End Page Down Intervals: 3.5 Intervals: 5 Intervals: 6 Intervals: 7 Selections: 2.3 Selections: 1.O Selections: 0.3 Selections: 0.2 ExtendIStop Home Up Paragraph Intervals: 4.5 Intervals: 6 Intervals: 7 Selections: 2.0 Selections: 0.2 Selections: O Up Line Page Up Intervals: 5.5 Intervals: 7 Selections: 0.6 Seiections: O Figure 5-3: On-screen keyboard re-design for frequency-of-use with Strategy 1 . 5-45.? Strategv 2: Scanning Text Keys A total timr of 4 1.4 sec. can be calculated for the re-arranged layout shown below versus 18.1 sec. for the standard layout. for a saving of 14%. ExtendlStop Down Para Down Line Left Intervals: 2 Intervals: 3.5 Intervais: 3.5 1 Intervals: 5.5 Selections: 2 Selections: 1.3 Selections: 1.O Selections: 0.6 Right Left Word End Page Down Intervals: 3.5 Intervals: 5.0 Intervals: 6.0 1 lntewals: 7.0 Selections: 1.O Selections: 0.5 Selections: 0.1 Selections: O Right Word Home Page Up Intervals: 4.5 Intervafs: 6.0 Intervals: 7.0 Selections: 0.8 Selections: 0.1 Up Line Intervals: 5.5 Selections: 0.2 Figure 5-4: On-screen keyboard re-design for frequency-of-use with Strategy 2. 5.4.5.3 Strategy 3: Sequential Scanning Text Keys A total time of 38.3 sec. can be calculated for the re-arranged layout show below versus 18.6 sec. for the standard layout for a saving of 2 1 %. ExtendIStop Down Right Word Intervals: 2 Paragraph Intervals: 4.5 Selections: 2.0 Intervals: 3.5 Selections: 0.04 Selections: 1.5 Down Line Intervals: 3.5 Selections: 0.4 Figure 5-5: On-screen keyboard re-design for frequency-of-use for Scan Strategy 3. 5.1.5.4 Strategy 4: Scanning Text A total tirne of 39.8 sec. can bc calculated for the re-arranged layout shown below vrrsus 50.1 sec. for the standard layout for a saving of 2 1 %. ExtendlStop Down Right Word Intervals: 2 Paragraph Intervals: 4.5 Selections: 2.0 Intervals: 3.5 Selections: 0.04 Selections: 1.5 Down tine Intervals: 3.5 Selections: 0.4 Figure 5-6: On-screen keyboard re-design for frequency-of-use for Scan Strategy 4. 5.4.6 Errors Under and ovenhooting the target occasionally occurred with Strategies 1 and 2, but it was easily corrected. With Strategy 1, such an error was the result of an error of judgement or selection of the wrong key. With Strategy 2, subjects had to closely monitor the scaming text cunor to ensure that it did not overshoot the target point. While subjects did not report much dificulty with this. they occasionally lost attention resulting in an error. A different type of error arose with Strategy 2 when subjects were confused between the repeating and non-repeating keys ( Under and overshooting adversely affected performance for Strategies 3 and 1 by requiring more than one keystroke that otherwise could have been sufficient. With Strategy 3. overshooting occurred when the subject did not correctly anticipate activating the selection switch just before jumping over the target. Subjects reported the stress of continuously comparing the position of the scanning text cursor with respect to the target point lead to such errors. Errors also occurred when subjects became confused when stepping down through scanning levels. This was reported to be difficult because until the text cursor started moving, subjects were unable to tell what the next movement would be without a careful mental note and counting of switch activations. With Strategy 4. overshooting occurred when the subject lost attention and did not follow the rule of activating the select switch when the target was highlighted. However. subjects generally reported that selection was quite easy and fewer errors were observed than with Strategy 3. Stepping down through levels was less of a problem with Strategy 4 because the visual feedback of the scanning highlight immediately informed the subjects of the expected outcome. Undershooting occurred with both Strategies 3 and 4 when the subjects activated the switch too quickly. To determine the frequency of errors with Strategies 3 and 4. the key history data were examined for additional keys to move forward (indicative of undershoot; Table 5-5) and additional keys to move backwards (indicative of overshoot; Table 5-6) in reaching the beginning and end points. Each such key was counted across subjects and trial pattems (2 trials x 5 subjects x 25 pattems = 250 maximum count) for each strategy, session group (to consider learning), and target point. ( Beginning Point 1 Strategy 3 1 Strategy 4 1 1 Session Group 2 1 8 1 t O 1 1 End Point 1 Strategy 3 ( Strategy 4 1 Session Group 1 32 13 Session Group 2 27 4 Table 5-5: Count of instances in which the subject undershot the target with Strategies 3 and 4. Beginning Point Sttategy 3 Strategy 4 Session Group 1 66 48 1 Session Group 2 1 65 1 35 1 -- End Point Strategy 3 Strategy 4 Session Group 1 62 22 Session Group 2 53 17 Table 5-6: Count of instances in which the subject overshot the target with Strategies 3 and 4. Strategy 3 had a total of 2461'1 000 overshoots and 8311 000 undershoots. Strategy 4 has a total of 1 12/ 1 000 overshoots and 45,' 1 000 undcrshoots. An ANOVA indicated no sipifkant di fference between Stratrgy 3 and 1 in undershooting but users of Strategy 3 overshot the target more than Strate3 4 usrrs (F( 1.3)=55.7 1: P~0.0017). There were no significant differences between session groups in ei thcr undershoot inç or overshooting, and there were no si gni ficant di fference between undershooting the beginning and end points. However. there was greater overshooting (F( 1.3)= 13.04: P<0.0225) of the begiming point than the end point. This suggests that users paid greater attention to selecting the end point than the begiming point. Correcting undenhooting was not perceived as difficult with either Strategy 3 or 4 because it maintained forward movement that was easy to control. However, correcting overshooting beyond a few characten was dificult, especially while extending the selection swith Strategy 4. The target remained highlighted when blocks were scanning backwards ahead of the target. Therefore, the rule for activating the switch when the target was highlighted did not apply. Subjects reported difficulties with planning and executing such crror correction. This was lsss problematic when scanning bac kwards at the character level. 5.4.7 Cornparison of Scanning Strategies vs. Standard Strategy Performance improvements in the total nurnber of keys selected with Strategies 2-4 with respect to the standard keystroke strategy are shown in Figure 5-7.In this figure two sets of data are shown. One set indicates improvements over Strategy 1 as observed in the experiment. The second set of data indicates improvements that are predicted based on optimal error-free movements with rach strategy, including Strategy 1. Here. it is clear that evrn if subjects wcre to improve their planning and choice of keys. the proposrd text scanning strategies remain consistently advantageous in reducing the number of keys. lmprovernent Over Standard Keystrokes: Total Keys 80% Expenment Strategy .Optimal Predictron Figure 5-7: Performance improvement in total keys with Strategies 2-4 over standard keystrokes strategy observed in the experiment and predicted based on optimal error-free rnovements. Performance improvements in the total number of select switch activations with Strategies 2-4 with respect to the standard keystroke strategy are shown in Figure 5-8. This illustrates improvements as observed in the experiment and predicted based on optimal en-or-free movements with each strategy. Irnprovements are less than that shown for key usage because of the added switch activations associated with text scaming. lmprovement Over Standard Keystrokes: Select Switch Activations 6096 2 3 4 O Experirnent Strategy .Optimal Prediction Figure 5-8: Performance improvement in select switch activations with Strategies 2-4 over standard keystrokes strategy observed in the experiment and predicted based on optimal movements. Performance improvçments in the total times with Strategies 13 with respect to the standard krystrokrs strategy are shown in Figure 5-9. This illustrates improvements as observed in the experimrnt and predicted based on optimal error-free movements with and without optimal ksyboard layouts with each strategy. hprovernent Over Standard Keystrokes: Total Time 30% n Expriment 2 3 4 =Optimal Prediction Strategy goptirnal Layout Figure 5-9: Performance improvement in total time with Strategies 2-4 over standard keystrokes strategy observed in the experiment and predicted based on optimal error-free rnovements with and without optimal keyboard layouts. Important insight was gained into the tradeoffs made behveen user control and programmed strategies with respect to overall task time and user demands. The proposed strategies significantly reduced the number of keys to be selected and switch activations by relieving the user of some degree of control. In particular, Strategies 3 and 4 (which represented a single scanning opention) rninimized user intervention, but this came at a cost of sometimes inefficient scanning. Thus. the tirne savings were not as great as they were for the number of keys and switch activations. With Strategies 1 and 2, the user retainrd control in choosing efficient movements which helped reduced the overall time. 5.5 Discussion The structure. design. and view of the text selection task for each scanning strategy creatrd di fferent user dcmands that induced distinct performances. User demands inc luded plannins movemtnts and choosing the appropriate on-screèn keyboard key: attention to the task of scanning within and between the on-screen keyboard and the text area: choosing either the select or cancel switch as appropriate; and activating a switch within the assigned scan interval. Objective performance measures included specific strategies for moving io the beginning and end points of the text blocks through certain key selections: switch usage; overall time to complrte the task; and mors. Subjective measures included feelings of directness and control. frustration. and stress. The evaluations that were conducted should lead to better understanding of specific user strategies and induced mors that cannot be foreseen and which may influence the future design of scanning strategies. The following discussion is organized around the user demands and the impact that they had on the vanous performance measures for each of the scaming strategies. A summary of the issues is first presented in the Table 5-7 in ternis of pros and cons for each of the strategies. Strategy 1 Strategy 2 Strategy 3 Strategy 4 Pros 1 efficient jumping moves 1 less pressure to always make 1 minimal planning minimal planning possible efficient moves minimal attention shifting B minimal attention shifting cancel switch usage is for a 1 less stress in choosing next 1 one operation to reach a point B one operation to reach a point consistent purpose movement 1 possibility of savings with D consistent and easy to apply user maintains full control of al1 1 cancel switch usage is for a cancel switch at higher selection rule movements consistent purpose scanning levels B no confusion of scanning level B consistent with prior B user maintains control over D cancel switch safely used for experience of task choosing efficient inoves easy to track scanning pattern multiple purposes D easy to understand less likely to overshoot B user maintains feeling of direct control over moving text cursor user gains feeling of placing (not moving) text cursor Cons D rnuch planning required D confusion between repeating b constant concentration constant concentration and non-repeating keys required tracking text cursor required D stress imposed to quickly plan with respect to target the next move immediately B difficult to select a single tedious scanning across lines after a selection movement step with a B tedious scanning across lines user independence of repeating key 0 constant attention shifting confusion as to scanning level movement sequence lost between the text and the on- may overshoot target if not user independence of confusion stopping after screen keyboard, and between paying attention movement sequence lost overshooting; longer error time the text cursor and target point O tendency to overshoot target difficult to correct overshooting O many physical actions required except by characters because difficult to correct overshooting O repetitive actions viewed as selection rule no longer applies except by characters wasteful and tedious cancel switch usage confusing O slow with most time spent user loses feeling of controlting scanning keyboard movement of text cursor Table 5-7: Pros and cons of each of the scanning strategies. 5.5.1 PlanninglMovement Strategies Planning is a significant task with the standard keystrokes strategy because it must be done between every rnovement. The task of identiwing the begiming or end points of a selection involves several sub-tasks, each with a planning element. With every key selection. the task of getting to the target starts over. only with a shoner distance. Generally. subjects demonstnted a wide variation of different movement sequences with Strategy 1 (standard keystrokes). This was indicative of different styles of spatial problem-solving and greater available choicrs. It also suggests that much planning and mental spatial calculations wrre required to weigh various alternative movemrnts. Some subjects foliowed a conservative plan and moved from large to srnaller rnovements with few tactical jumps. The overall preferred rnovement strategy was to movs lefi-to-right. top-to-bottom, large movements to small. Planning efforts werc reduced with Stntegy 2 (scanning text keys). because the subjects only had to make a few decisions related to choosing appropriate movement keys. For example. subjects chose a single scanning key rather than repeatedly selecting it as required with standard keystrokes. However. there was a new demand of planning to stop the scanning text cursor before it jumped past the target. Fewer strategic jumping movements were employed becaause it required less effort to allow the scaming to continue across the text rather than plan altemate movrments. Subjects let the scanning text cursor do the work for them. Thrre was one primary movement planning task associated with Strategy 3 (sequential scanning text keys) which was to choose the correct movement key to initiate the text cursor scanning such that it did not irnmediately overshoot the target point. Scaming to the target was one continuous operation. Once the text cursor began scanning, however. subjects had to continually monitor the scanning and plan when to activate the select switch such that the target was not overshot, or to activate the cancel switch to take advantage of the block selection. With Strategy 4. the primary task of selecting an insertion point matched the planning required to make a scanning selection. Subjects did not have to plan when to stop scaming if they followed the nile of activating the select switch when the target was highlighted. Planning effort was lessened in cornparison to Strategy 3 because subjects could select the The planning effort required to correct error situations. however, was the inverse of the above descriptions. With standard keystrokes. there were only inefficient movement choices. Planning to correct such a choice was no different thrn ongoing movement planning. When correcting overshooting errors. al1 of the proposed text scanning strategies required additional planning. Strategy 2 usen had to plan to move back to the target either entirely through backward movement or by backward movement followed by a forward movement. Strategy 3 required more planning when the target was ovenhot past a word. Subjects had to determine the initial backward movement increment such that the tgxt cursor moved behind the cursor and then scanned forward. Strategy 4 had similar dçmands when choosing the beginning of the text selection. However. additional planning demands were imposed when targrting the end point as the text selection and scanning highlight were merged. Here. the nile of activating the switch whenever the tarset was highlighted no longer applied. 5.5.2 Attention When users plan 3 rnovernsnt, their attention is first drawn to locate both the targrt position and the current location of the text cursor. Afier deciding upon a movement key, users shifi their attention to the on-screen keyboard to scan through to select the key. They then shifi their attention back to the text area to detennine the oiitcome of that movement. These attention shifis are directly related to the numbrr of keys selected. With every attention shifi. there is the possibility that the user will forget their last decision (e-g.. movement to make or key just selected) leading to a potential error. Also, with every attention shift users must re-orient themselves to changes in screen activity. Within the on-screen keyboard. a delay on the first item of a new scanning group is typically implemented to accommodate such re-orientation as well as physical recovery. Within the proposed text scanning strategies. a similar delay was added to the first scan interval at each movement increment. The large number of key selections required wi th the standard keystrokes strategy generatrd constant attention switching between the text area and the on-screen keyboard. This added to the overall laborious nature of this strategy. Strategy 2 reduced the switching of attention between the on-screen keyboard and text area through fewer key selections. An attention demand was added. however. as users had to ensure that the text cursor did not overshoot the target. In one way. this attention was lessenrd by the fact that the text cunor and target were within close visual range. but attention still shified constantly between them. Strategy 3 minimized attention switching between the on-screen keyboard and the text area since only one key was required to reach any target point. However. constant attention was required throughout the text scanning. In contrast to Strategy 2, subjects did not have to dividr thrir attention between watching the text cursor and deciding the next move. As long as no mors were made. keys always altemated between a movement key and the extend/stop extend selection key. Strategy 4 was similar to Strategy 3 in terrns of minimizing attention switching between keyboard and trxt. It offered an improvement by rliminating the comparison between the moving text cursor and target, and by providing visual feedback of its scanning increment size. Howrver. attention demands went up tremendously when correcting an overshooting error with the end point as the selection nile no longer applied. With both Strategirs 3 and 4. subjects demonstrated an attention problem when scanning to get to a word near the end of a line. Because the comparison of the scaming at the word level with respect to the target point was not critical when distant to the target. subjects' attentions wandered. When the scanning approached the target, full attention was required but was sometimes too late for the subjects to react accurately. 5.5.3 On-Screen Key Usage Subjects using the standard keystroke strategy demonstnted effective use of the full-range of text keys and extended movernent keys such as Both Strategy 3 and Strategy 4 were very much pre-determined in ternis of user performance because only a single key was required as long as no error was made. Any differences with the predicted performances were due to mors in either undershooting or overshooting t hr target. Subjects quickly leamed that the extended movement keys had no value to them. Thosè subjects that tned to stop scaming and use a more efficient key found the effort too great and Iead to errors. Thus. they quickly gave up trying in the first session. Backward movement keys were only used to correct ovrrshooting brcause al1 scanning started at the lefi margin. 5.5.4 Switch Usage 5.5.4.1 Select Switch The prediction models best demonsrrate why Strategies 3 and 4 are advantageous in terms of select switch activations. For both of these strategies. the number of activations to position the insertion point anywhere in the text is at least 3 and never exceeds 6. In contrast, the number of select switch activations Vary in proportion to the total number of movement keys with Strategy 1 and less so with Strategy 2. For al1 strategies a total of four switch activations are required to choose the extendistop extend selec tion key. Overall. the improvement in number of switch activations with the text scanning strategies with respect to Strategy 1 remains substantial. This has great importance to users with disabilities, as excessive switch use is fatiguing and potentially harmful as it may lead to repetitive strain injury. 5.5.4.2 Cancel Switch With Strategies I and 2. the cancel switch was only used to cancel scanning within the on-screen keyboard if subjects missed their desired row or selected the wrong row. While the text cursor was scanning with Strategy 2. the cancel switch was functionally equivalent to the select switch. There was no 'undoing' of the movement with the cancel switch as there was in the on-screen keyboard. Therefore. subjects did not use the cancel switch while scaming text. Subjects using Stratem 3 leamed to use the cancel switch as a 'catch-all' for dealing with any situation in which they were confused or needed a relief fiom the stress of concentrating on the scanning text cursor. This reduced the srverity of any error by limiting the distance the tcxt cursor scamed past the target. The greater use of the cancel switch also lead subjects to the srlf- discovery that they could select a location as soon as it was reached without stepping through al1 scanning levels. This was an intended fùnction by design. At the higher scan levels this could Save select switch activations and task time. However, it was only usefùl when the target point coincided with the bcgi~ingor end of a large text object (Le., paragraph or Iinr). Subjects did not smploy the cancel switch to the samr degree with Strategy 4 becausr they did not view it as a 'safe' escape mechanism. The cancet switch lefi a block selected in the text area rathrr than a single text cursor. This resulted fiom the transparent keystroke approach which created a scanning highlight by holding down the With scanning access. task time is related almost entirely to the number of scaming steps to reach the target selection. Some individual variations are possible outside of the control of the scanning system. Rrsponse time within the scan interval can increase or decrease the overall time by the nurnber of selections times the average difference between the actual rrsponse rimes and the midpoint used in prediction calcuIations. Clearly. if the user could respond faster. a shoner scan interval could proportionally reduce the time for every selection. However. shonening the scan interval for a user who has a physical disability may not be feasible. Other variations include response time to recognize an error and stop scaming. and waparound scanning across rows or columns which is a factor of the number of row or column steps. Scanning steps occur within the on-screen keyboard and within the text area in the case of text scanning. Each of the proposed text scanning strategies offered time savings with respect to the standard keystrokrs strategy by reducing the steps taken in the on-scrern keyboard, which in this expenment varied between two and eight. Within the text arra. each movement was a consistent sin&-step except for the first movrment increment that had a delay equal to two steps. With the standard keystrokes strategy every movement requires a selection in the on-scrrrn kryboard which may take several scan intervals. With Stratrgy 2. time is only spent scanning the keyboard when a different size movement is needed and to select the extend'stop extend selection key. Overall time is reduced since fewer keys are needed. There is only one movement key that nèeds to br selected with Strategies 3 and 4, hence most of the scanning is done within the text area. Although it was predicted that timing would improve slightly with these strategies with respect to Strategy 2. it was not observed in the experiment. The slower performance was due to en-ors that occurred with Strategies 3 and 4. A significantly slower time for Strategy 4 than predicted and with respect to Strategy 3 was unexpected. especially since this strategy used fewer keys and switch activations, and had fewer èrrors than Strategy 3. The reason for this slower time was that subjects had difficulty stopping the scanning text when the target was overshot. As a result, subjects had to scan farther back to makr a correction. Only a slightly slower time had been expected due to the prograr-nming of this strategy where scaming brgan at the current position and not afier moving one position. The continuous scanning afier each selection created some timing probiems for the subjects with the standard keystrokes stntegy. Afier every selection. the subjects had to complete their planning to choose the next key while the first row was scanned. As discussed before. this required attention shifiing and analysis of the situation. Scanning wraparounds that resulted from the subjects being unable to accomplish the planning in time detracted from any timing gains made with stntegic moves. An appropriate delay on the fmt row could help alleviate some of this stress. The obsened reduction in time fi-om the first to second session group can be accounted primarily io fewer wraparounds which suggests that through expenencr. users cm leam to plan more quickly. This also suggrsts that it may be appropriate to increase the delay on the first item for new tasks. Time loss due to wraparounds in the on-screen keyboard with Strategies 3 and 4 was less likely because so few keys were chosen and planning was minimal. There are drawbacks to the proposed strategies that detract from their potential tirnrsaving. Whilr subjects using Strategy 2 considered timesaving moves to jump across a linr. they often chose a repeating keystroke and waited for the text cursor to scan across. Whatrvsr use the subjects made of strategic movements did not reduce the overall time in cornparison to conservative movements. There was only a small improvement that can be accounted through faster srlections. Subjects using Strategies 3 and 4 accepted waiting while scaming across items that might otherwise have been jumped. Although subjects had the opponunity to potentially stop the flow of scanning to choose other keys, they realized that it would incur a time loss and mental effort figunng out altemate moves and scaming through the on-ssreen keyboard. This demonstrated that given the choice. the subjects preferred to minimize their efforts. A limiting factor on overall tirne with Strategies 3 and 4 was that subjects could not take advantage of the relative horizontal position of the end point with respect to the starting point as was the case with both Strategies 1 and 2. Thus. time gained by reducing the number of keys selecied from the on-screen keyboard was lost with inefficient movernents. 5.5.6 Errors Errors associated with the standard keystrokes strategy related to either selecting the wrong row in the on-scrern keyboard or choosing an inefficient key. The former error was correctrd by activating the cancel switch to restart scanning The latter error. which reflected upon the judgrnent of the user not on the strategy itself. was corrected by choosing another key to bnng the user back on track in moving towards the target point. With Strategy 2. subjects sometimes emed in selecting the wrong on-screen keyboard row. This was corrected by activating the cancrl switch to restart scanning. Other errors included stopping the repeating movement too early (undershooting)due to over anxiousness, or too late (overshooting) due to losing attention. and confusing repeating and non-repeating keys. The latter error rnight be reduced through better visual feedback distinguishing the two types of keys. The experimenr revralrd unique erron with Strategies 3 and 4. Subjects were sometimes confused by the lack of feedback with Strategy 3 indicating the current scanning level. This caused difficulties when moving through more than one lrvel (ç-g..paragraph to word) that resultrd in overshooting the target as scanning continued afler the subjects thought they had stopped it. Overshooting also occurred when the subjects did not correctly anticipate stopping the text cursor before it jumped past the target. Undenhooting occurred when the subjects activotrd the switch too soon. not wanting to jurnp past the target. Stratem 4 had fewer such mors because of the easy and consistent rule of activating the switch as soon as the target was highlighted at al1 scanning levels. Errors occurred nonetheless. These can be attributed to losing attention to the task. Attention was more likely to wander when scanning across many words in a line and there was a long time delay before the target was reached. Comcting an overshooting error with Strategies 3 and 4 was more dificult because subjects had lcss experience with reverse scaming. The sequence of backward scaming followed by fonvard scaming for correction was awkward. In cornparison, subjects using Strategies 1 and 2 gained much more experiencç with reverse scanning because half of the tasks required backward movement to get to the end target points. Also, the single text step backward movement was easirr to unders tand t han the sequence of backward and forward steps. 5.5.7 Directness The standard keystroke strategy maintained a farniliar typing metaphor to accomplish the task of rnoving the text cursor. As such, subjects maintained a feeling of directness in controlling the text cursor because every movement was their individual choice. However. overall directness to the pnmary task of setting the insertion point was lost because every movement was a distinct task and only in the last movement did the scanning operation relate directly to the task. Strategy 2 maintained the user's virw that they were using the keyboard to move the text cursor rven though the text cursor scamed. Subjects considered this to be a fom of kry repeating with which they, as able-bodird users. were quite familiar. A feeling of direct control over the scanning was maintained because the subjects chose each different movement. While brevity improved. each movement selection remained a distinct task. thus reducing ovrrall direcmrss. It had been intended that users of Strategies 3 would perceive a feeling of directness approaching the lrvel of selscting items from the on-screen keyboard. It was also intsndsd that subjects would develop an associated mental model of an independent scaming text cursor. This strategy offered minimal planning and user intervention. and the text scanning was a familiar single operation as in the on-screen keyboard. However. subjects maintained the pnmary view that they were selecting keystrokes. albeit linked. It is suggested that a number of factors contributed to this perspective: the strength of the visual feedback. the keyboard display of trxt keys. and lirnited control over the scanning text cursor. This detracted from the overall directness of this approach. Although Strategy 4 involved similar grouping of movements as Strates 3, the associated view of the task was quite different. Rather than moving the text cursor, subjects selected the target insertion points through scanning. The impact of this on the subjects' perception of control was that they lost some feeling of directness over controlling the text cursor. It had been intended that the subjects develop a mental model that reduced the role of the text cunor to a place marker. However. prior trxt editing experience and expectations of moving the text cursor rernained a strong influence. Thus. even though this strategy best matched the scanning on-screen keyboard and offered direc tness, it remains questionable whether the model was appropriate. Three new strategies for positioning the insertion point by scaming the tex Time improvemrnts were not as substantial with the proposed text scaming strategies. This suçgests that the number of text selection tasks that can be accomplished within a certain time period may not necrssanly be much greater than not using those strategies. However. the rase by which text selection is possible with these scanning strategies may mean that they will increase the range of people that can perform more difficult or demanding editinç tasks. .4n important tradeoff factor with respect to overall time was the degree to which the user had control over scanning events. Error handling was a particular problem associated with two of the three strategies that othenvise offered the greatest benefits. -4.5 npected. the standard keystrokes strategy was the slowest. used the most on-screen keys. required the greatest number of select switch activations, and resulted in constant attention switching between the text area and the on-screen keyboard. Subjects demonstratcd an ability and a strong desire to apply strategic moves to reduce the number of selected keys. The scanning text keys strategy significantly reduced the number of key selections and switch activations. It was easy to use and subjects had control over al1 text cursor movements. Time was reduced by approximately one-fifih. A particular usability problem was confusion between repeating and non-repeating keys that were available on the on-screen keyboard. The sequential scanning text keys strategy substantially reduced user demands. A drawback was that the users did not have control over the direction of movement resulting in some inefficient movements and a feeling of some loss of control. Planning and attention switching between the text area and on-screen keyboard were minimized. Tirne savings were. however. equivalent to the scanning text keys strategy. This strategy had some specific dificulties including extra vigilance to constantly compare the location of the text cursor with the tarset location: confusion rrgarding the current scaming Irvel: and error correction. The text scanning strategy had sirnilar efficiencies as the previous strategy with fewer errors of over and undershooting because of the easier selection rule and the visual feedback of the highlighting block that indicated movement size. However. time performance was poorer becausr it was more difficult to stop scaming after overshooting the target and it took longer to make corrections. Although consistent with scanning the on-screen keyboard. subjects felt loss of control over the cursor as they retained a text cursor mental model. Wi th the latter two strategies. experience should reduce errors and the associated correction task. but key selection and switch activations are already minimized. With al1 stratepies. timing can br improved through a rearrangement of keys in the on-screen keyboard to reflect frequency-of-use with no added demands on the user except the initial leaming of key positions. A limitation on timing irnprovemsnts is the fixrd lefi-to-right scaming of these strategies. particularly when scaming across many items. This particular limitation is examined in the next chapter in an evaluation of overdrive scanning. One of the rnost significant factors for users with disabilities with both Strategies 3 and 4 is the reduction in switch activations as excessive switch use is fatiguing and potentially harmful. It is not suggested that any one strategy is 'best.' Al1 strategies work within the task transparency concept. Improvements seen with Strategies 3 and 4 cm have a significant impact in minimizing the physical and cognitive demands of switch-based scanning. However, the costs associated with specific attention requirements. error correction, and inefficient scanning sequences suggest that further work is required to refine the strategies. Also, the specific abilities of the user will dictate what strategy is most appropriate for them. Overdrive Scanning Evaluation 6.1 Introduction This chapter describes and discusses the evaluation of overdrive scanning as a potential method of rcducing time spent scanning across many items. A frustration that was envisioned and reponed by the subjects in the previous experiment with the text scaming strategies was the tedium of scanning across a line of words. This was because the sequential scanning text keys and scanning text strategies always scamed words fiom left-to-right staning at the lefi margin. Although it was possible for the subjects to stop the scanning and jump to the end of the line. thsy did not do so brçause it broke the flow of scanning. This observation subs tantiated the need to consider some addi tional method(s) to reduce 'wasted' scanning timc. Ir also contributed to the insight that the degree to which the user has conirol over scaming events is an important tradeoff factor with respect to overall time. As user control is reduced by prc-programming strategies. time is lost dus to inefficiencirs in such strategies. Since the reduction in drmands arising fiom those strategies is desirable. a question remains whether any fûrther reductions in time can be made by giving back some control to the user. in panicular. with regard to the scan interval. Overdrive scaming was descnbed in Chapter 3 as a potential solution. Overdrive scanning involves the user intentionally shortening the scan interval. An experiment was camed out to identify usability issues. Analyses using performance data obsrrved in the experiment were also performed to compare overdrive scaming with sequential scanning text keys. 6.2 Methodology 6.2.1 Goal The goal of' this experiment was to explore and quanti@ the usage of the two di fferent methods of an 'overdrive' scanning control to decrease the time takrn to scan across an array of items. Both overdrive methods used two switches for scaming control. A 'select' switch stopped the scanning highlight when it reached the desired target. An 'overdrive' switch advanced the highlight over the items at a faster rate. With Method 1. users held down the overdrive switch to shonen the scan interval that caused the scanning to proceed faster across the array. Whrn the switch was rrleased the speed slowed to the original rate. With Method 2. the user clicked the overdrive switch to toggle the scan interval to a shoner time for faster scanning. When the switch was clickrd again. the speed slowed to the original rate. A number of specific questions were addressed for each method: ( 1 ) At what distance away (number of items scannrd) From a staning point do usrrs dccide take advantage of overdrive? (2) When do users initiate overdrive once they decide to use it? (3) Whrn do users stop overdrive? (1) What are the tirne savings of overdrive compared with regular item scanning? (5) How does overdrive rate affect performance'? (6) When do mors occur? 6.2.2 Experimental Design A between-subjects design was employed utilizing two groups of ten able-bodied subjects each in this experiment. Each group used one of the two overdrive methods in four sets of trials. The subjects' task was to select the target item presented in the experimental application (see Section 4.4). Users were instructed to use overdrive scanning to help them move to the target location as quickly as possible while maintaining accuncy in selecting targets (Appendix H). They were to only use overdrive scanning when they felt confident that they could accurately select the target. Each of the four sets of trials performed by each proup included 30 test trials in which each of the fifieen targets were trsted twice. Thus. each set incorporated at total of 300 observations: 20 observations per individual target item. Overdrive scanning was not used in the tirst set that served as a baseline. In each of latter three sets, subjects used overdrive scaming at different speeds. The specific order for using different speeds was chosen through a random drawing and varied betwern subjrcts. The base scanning rate was set at 0.66 seconds/item. This rate was chosen as slow enough for al1 subjects to accurately select al1 targets. yet fast rnough that it demanded attention to the task. Overdrive rates were set as factors of this base scan rate: Zx (0.3 src.!item): 3x (0.2 sec.!item) and 6x (0.1 I seciitem).' Subjects were providrd with practice with each scanning rate. Prior to the first set. subjects had 15 practice trials in sslrcting targets without an overdrive switch. Additional practice was not nrcessary because of the simplicity of this baseline task. A minimum of 30 practice trials preceded each of the other sets following a shon break in which instructions were rcviewed. If subjcct performance was less than 90%. they were allowed additional 30 practice trials. Al1 subjects used idcntical switchrs. Subjects used their dominant hand to activate both switches that were placed directly in tiont of them on a desk where the keyboard is norrnally placcd. The keyboard was positioned off to one sidr for the researcher to control the opçration of the software. The researcher only intervened if there was a physical problem (such as a switch not properly activating). Any trials with such an intervention were repeated. Upon completion of the last set. the subject identified their preferred overdrive speed. They were also asked to describe how their attention vaned between sets as well as any other general cornments. ' .4ccuncy of the scanning rate within WiViK was 1:'18 seconds which was the standard MS Windows 'tick' count 6.2.3 Su bjects The twenty subjects were able-bodied with no motor. cognitive or visual-perceptual deficits that would interfere with the tasks. Staff members at the researcher's institution were employed. Some had panicipated previously in Experiment 1. None were aware of the particulars of this expenment prior to being requested to panicipate. The subjects were asked to sign an informed consent form after reading an information sheet. The hypotheses of the researcher were not disclosed to the subjects until afier completing the experiment. It was expected that individuals with motor impairments might exhibit different physical behaviours than those who panicipated. Potential differences include a slower reaction time. inconsistent responsrs. and reflex overtlow (muscle spasms) when switching control from one switch to another. However. an assrssment and prescription of multiple switches would endeavour to choose appropnate type and placement of switches. and setting of scan rate such that performance nrarly equals that of a person without disability. 6.3 Results 6.3.1 Use of Overdrive To determine the distance away (number of items scanned) from a starting point that users decided to take advantage of overdrive. the data were first soned for each target position of the 15 items in the target array. Then for each target position. individual times per item were rxamined for overdnve usage that was evident by scan interval times less than the standard scan interval of 0.66 sec. A target was then marked as having used overdnve or not. For each target position, a count of overdrive usage was made across al1 subjects within a group. Thus. for each position and trial set per group, there was a maximum of 20 data points ( 1 O subjects x 2 data points per position). A percentage usage (sumf20x 100%) was then determined. These data are show in Figure 6-1 and detailed in Appendix 1. Overdrive Usage (Method 1) Target Rem (distance) Overdrive Usage (Method 2) 12 3 4 5 6 7 8 9 10 il 12 13 14 15 Target item (distance) Figure 6-1 : Usage of the overdrive with respect to distance of target items and overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.) for both methods The obsenred data suçgest a tradeofffunction. There are three zones in the target array for which the subjects decided whether or not to use the overdrive function. The first zonr ('no') is over the first few items. Here. the subjects irnmediately decided. with minimal conscious effort. not to use overdrive (0% use). In the next zone ('maybe') the likelihood of using overdrive increased with target distance and subjects reported that they had to make a conscious effort to considrr whether to use overdrive and still accuratel y select the target (>OO/O and < 1 00% use). The third zonr ('yes') is over the distant targets and the subjects always used overdnve ( 100% use). These usage zones are shown in Table 6-1 as number items fiom the staning point to the target. 1 1 Overdrive lnterval 1 0.33 0.22 0.1 1 Method 1 <3 1 3-5 1 >5 <3 13-5 1 >5 <4 / 4-6 !>6 Method 2 c4 1 4-8 / >8 <5 1 5-9 / >9 c6 1 6-9 1 >9 Table 6-1 : Usage zones of overdrive. During the experirnrnt. it was obsrrved that subjects initiated overdrive almost immediately once thry decided to use it. The data were reviewed to determine this more precisely. For al1 targets in the 'yes' zone the scan intervals of the second. third and founh item were e'ramined for overdrive being initiated on the first. second or third item. (Note: The overdnve scan interval was applied after the interval it was initiated.) Figure 6-2 illustrates the proportions of tdsin which overdrive was initiated in sach of these first few positions. Method 1 Overdrive Starting Points Method 2 Overdrive Starting Points O 33 0 22 0.1 1 O 33 0 22 Olt Overdrive interval Overdrive tnterval Figure 6-2: Proportion of observations within the 'yes' zone in which overdrive scanning began during the first, second and third or greater item scanned for each overdrive interval. These data indicate that overdrive was mostly initiated on the first item with Method 1. and on the second item with Method 2. There was no statisticai difference between overdrive scanning iniervals with each mcthod (%'<1 ). In addition to leaming the initiation point for overdrive. the ending point was also determined. A similar procedure as above was applied in which counts were made just before the target within the 'yes' overdrive zone (Figure 6-3). Method 1 Overdrive Ending Points Method 2 Overdrive Ending Points Overdrive Interval ûVefdr~eInterval Figure 6-3: Proportion of observations within the 'yes' zone in which overdrive scanning ended during the first. second and third or greater item before the target for each overdrive interval. While it was noted previously that the starting point for initiating overdrive was relatively consistent. there is a visible trend towards releasing overdrive earlier as rate increases. .4t the slowest overdrive rate. subjects used overdrive until one or two items before the target. and two or three items before with the faster rates. 6.3.2 Time Savings The time savings that overdrive offered was calculated in two steps. First. the total time to complete each trial was extracted from the data for each target item. Then, the total times for each of the three overdrive rates were subtracted fiom the baseline time when no overdrive was used for each target item. The total times for each trial were soned for each position of the 15 items in the target array since they were presented randomly. The times were then averaged for each target item. each trial set. and each group of subjects. Only successful trials were included. Thus. for each position and trial set per group. there was a maximum of 20 data points ( IO subjects x 2 data points per position). Selection time (response time to target being highlighted) was 0.4 sec. on average. There were no significant differenccs in selection time benveen methods or overdrive scan interval (X' By considenng the set of trials without overdrive as a baseline, overdrive data can be presented in terms of time savings relative to the baseline for each target item ([Overdrive Time - Baseline Time]/ Baseline Time). These data are show in Figure 6-4 which plots for each method. the relative time savings versus target item for each set of overdrive trials: 0.33 sec. overdrive scan interval: 0.22 sec. overdrive scan interval: and O. I 1 sec. overdrive scan interval. These data correspond to the overdrive usage zones. In the 'no' zone thrre is obviously no benrfit. In the 'maybç' zone there is a rapidly increasing savings as the target distance increasrs. In the 'yes' zone thrre is slightly increasing time savings with distance approaching savines in the order of 40-60°& While these time savings data illustrate that Method 1 begins to offer savings for closer targets than Method 2. rhere is little difference for the last several targets between methods. Method 2 is marginally slower for these latter targrts which can be rxplained by overdrive scanning starting tater and ending earlier. These data illustrate several points. Fint, time savings with overdrive do not begin until afier the first few irems as illustrated previously with the usage zones. Such reductions begin earlier with Method 1 than with Method 2. Second. the total time to cornplete the task does not Vary much between more distant items for the faster overdrive speeds. This is to be expected when the overdrive is used brcause the time scanning across items is quite small with respect to the ordinary scan rate. Time Savings with OverOrive (Method 1) TU- nem cdbtana) Time Savings with OverOrive (Method 2) Targa Rem(distance) Figure 6-4: Relative time savings to select target items for both methods and for the three overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.). In terms of reai-tirne savings, there is little benefit of using the overdrive in the 'maybe' zone. In cornparison. it is apparent that the 'yes' zone provides a clear and relatively consistent advantage over not using overdrive. This is supponed by verbal comrnents provided by the subjects upon completion of the trials. A real time savings of several seconds is possible in this zone. 6.3.3 Errors Selection mors wcre genenlly low. although Method 2 appeared to have more errors that increased with fasrer overdrive rates. However, a Chi-squared analysis of these data did not demonstrate a significant difference (%:= 7.30; Pc0.0630) between Method 1 and Method 2. Emor scores are shown in Table 6-2 that lists total number of errors observed for both methods for each overdrive level(300 observations each). The distribution of errors for each target item is show in Figure 6-5 based on 20 observations per item. 1 1 Overdrive lntenral 1 Baseline 0.66 0.33 0.22 0.1 1 Method 1 2 11 2 11 Method 2 4 11 17 23 Table 6-2: Total selection errors for both Methods, for the baseline and for the three overdrive scan intervals (0.33, 0.22 and O. 1 1 sec.). Selection Errors (Method 1) Selection Errors (Method 2) Target (diance) Target (distance) Figure 6-5: Distribution of errors for each target item for both methods and for the three overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.). Here. errors are more evident in the 'maybe' zone for both methods. There were no errors with the mid-speed overdrive using Method 1 on the Iast five targets. On those same targets with Method 2. there is a relatively consistent number of small errors at al1 overdrive speeds with the fastest having slightl y more errors. 6.3.4 Subject Reports Al1 subjects in both goups reported that they preferred having the overdrive function available especially for more distant items. Their specific preferences are reported in Table 6-3. Overdrive Interval 0.33 0.22 0.1 1 Method 1 1 2 7 Method 2 1 6 3 Table 6-3: Number of subjects who preferred specific overdrive scan intervals (0.33, 0.22 and 0.1 1 sec.) with both rnethods. With Method 1. most subjects preferred using the 6x overdrive rate (O. 1 1 sec. overdrive interval) over the othrrs. With Method 2 most subjects preferred using the 3x overdrive rate (0.1 1 sec. overdrive interval) over the others. Subjects could notice sorne benefit of a 21 overdrive rate (0.33 sec. overdrive interval) but the added physical and mental demands ovenveighed the benefit. An interesting report by al1 subjects was that the overdrive improved their concentration on the task. Scanning to distant targets without overdrive was tedious and they felt that they were easily distracted. The overdrive demanded full attention throughout the whole task. which they reportrd gave them a greater sense of independent control. 6.4 Discussion This experiment demonstrated that the subjects were able to use two rnethods of overdrive scanning to reduce scanning time. Method 1 required a holding action. and Method 2 required two discrete switch actions to toggle the overdrive. Both methods provided improvements over not using the overdrive for a certain range of targets. AI1 subjects developed a common strategy for using overdrive. Over the first few targets in the array, subjects quickly leamed that the overdrive was too difficult to toggle odoff and offered no benefit. For these items, they immediately decided not to use the overdrive ('no' zone). Over the last proup of targets, subjects immediately toggled the overdrive on with little thought ('yes' zone). Targets in between these two zones were considcred as potential candidates for using overdrive. but this required some mental consideration ('maybc' zone). Usage in this latter 'maybe' zone varied betwren subjects and method, and was of minimal benefit because of small time savings and mors. With Method 1, the 'yes' zone occurred earlier than Method 2. This was due to the differences in physical and mental efforts required toggling the overdrive. Method 1 used one continuous action and Method 2 used two discrete physical actions. These latter two actions required additional physical and mental effort. Afier clicking the overdrive on, the subjects had to hold their hand above the switch in a state of tension ready to click it off. Whrn the time between clicking on and off was short. subjects had difficulty timing the two-click action. Hence. subjects did not use Method 2 until the tareet was distant enough such that the 'between click time' was long enough to track the moving highlight and to make the effort to stop it before the target. Although this suggests that Method 1 might be preferable over Method 2, it is recognized that this result might not carry over ro al1 users with physical disabilities. The holding action may be quite difficult to releasr reliably if the user has spasticity. Similarly, the two clicking actions of Method 2 may be difficult for users if the time between clicks is too short. The delay in initiating overdrive with Method 2 by one scan interval may be attributed to the fact that the subjects sprnt more time deciding whrther or not to use overdrive because of its drmands. This decision time camed over into the 'yes' zone. It should be noted rhat in this cxperimenr. the first item scannrd was not delayed. If there is such a delay. it is expected that users would be able to initiate overdrive on the first item with Method 2. With on-screen keyboard scanning and Strategy 4. users generally focus their attention on the target and wait until it is highlightzd before activating the select switch. In this expenment, this changed with overdrive usage; subjects visually tracked the highlight and constantly compared its position with the target as they would with Strategy 3. They leamed to release the overdrive a specific number of items ptior to the target. With the fastest overdrive rates, subjects in both groups released overdrive on the third item before the target. Because of the nature of the WiViK scanning control, it would appear that the moving highlight had some 'inertia' and would take two locations to slow dom. This was because the highlight was moving so fast that when the overdnve was toggled off, the next item was already being scamed (at the faster rate). and the slower rate would not start until the item afier that. Al1 of this added to the demands on the user, but they reported that their aaention to the task improved and hstration was reduced. Overdrive required very good timing control, esprcially at the highest rate when the highlight might move across four items during the average responsr time. When considering the response time and the distance the highlight might travel. it is clear why the 'yes' zone is several items distant from the starting point. This nises the issue as to whether overdnve has any use at all. If the amy size to scan is always in the 'no' or 'maybe' zone of overdrive usage. then certainly overdrive would not be useful. For typical scanning of a few parakmphs. lines. words. and characters. this is the case. Thus, the original premise suggested at the begiming of this chapter that overdnve can reduce 'wasted' time spent scanning rnight be irrelevant if items were always scanned in small groups and there is no 'wasted' tirne within any one goup. However. there are some situations whcre time spent scanning certain groups might be considered 'wasteful.' As an example of potential wasteful scanning by groups. consider the following situation. Suppose the text cursor is near the end of the last line of a paragraph and the next edit requires selecting a word (say fifih or sixth) in the first line of the next paragraph. With sequential scanning tent keys the user would choose 'nrxt pangraph' to scan. The user would then select the next paragraph highlighted, select the first line, and then scan across several words before srlecting the desired word. None of these groups would be large enough to tngger overdrive. Aitemately. a simplrr item scaming method by words could be used with overdrive because the target word now falls in the 'yes' zone. T'his might be faster and offer greater control. There is a tradeoff situation in which overdrive is advantageous in some instances and not in others. This can be illustrated by comparing expected times using overdrive at an item scanning level versus expected times using one of the proposed scaming strategies. such as the sequential sca~ingtext keys. It is possible to derive an equation to predict total time when overdrive is used. Three assumptions are made. First, overdnve is initiated within the first scan interval with Method 1 and within the second scan interval with Method 2. Thus, if the first scan interval is doubled to offer a delay simiiar to that used in scanning text keys. then both methods can initiale overdrive within a longer fint scan interval. Second. overdrive is used throughout al1 but one item before the target. Third. the selection or response time is approximately % of the repular scan interval as used in predicting text scaming tirnes. Let T = target distance (number of items to scan) Sr = regular scan interval So = overdnve scan interval Tinlr = 2 x Sr +(T- 3) x S,, +Sr + K x Sr Tirne=;%x Sr +(T -3)xS,, It can now be demonstrated that overdrive is more advantageous when one group dimension to be scamed is lager than the others. This is illustrated in Figure 6-6 which plots predicted time savings to select words using overdrive scanning at the word level with respect to sequrntial text scanning of 5 lines and 15 wordsAine. Theoretical Time Savings with OverDrive -120% 1 1 Target hem (distance) Figure 6-6: Theoretical time savings to select words using overdrive scanning at the word level with respect to sequential group scanning of 5 Iines and 15 words/line. In this figure, the first six items take the same time to reach because both mrthods would use item scanning at the word level. The dramatic dips in the plot indicate the first word of a nrw line. Here. the advantage of overdrive scanning over the group sca~ingis clear for the latter words of the line although this advantage reduces with each line. In the second line. 1 1 words have a time savings of 20°/0 or better: in the third line. 8 words have a similar rime savings: and in the fifth line. only the final 3 words have such an advantage. The advantage of üsing overdrive drops faster when the group sizrs are more equal. This is illustrated in Figure 6-7 which plots predicted time savings to select words using overdrive scanning at the word level with respect to sequential group scanning of five lines. threr word 2~oupsiline. and fivr wordshord goup. A 6x overdrive is also used in this example. It was assumed that overdrive began on the seventh item. and al1 items but one. in addition to the tirst and last targrts. were scamed with overdrive. Here. a time savings of 20°h or bettrr is only to br rxpected in the latter half of the first two lines. Theoretical Time Savings with OverDrive Tar get hem (distance) Figure 6-7: Theoretical time savings to select words using overdrive scanning at the word level with respect to sequential group scanning of 5 lines, 3 word groupslline; and 5 words/word group. 6.5 Summary This second evaluation studied two variations of a method. overdrive scaming. employing a second switch under user control to scan more quickly across an anay of items. Overdrive scaming can be applied to any of the text scanning strategies to potentiall y reduce scanning timr. One overdrive method required a holding action and the other method required two discrete switch actions to toçgle the overdnve. With both methods. there was a clear tradeoff function associated with using overdrive. There were three target distance zones in which subjects demonstrated overdrive usage: a 'no' zone in which the user would definitely not choose overdrive: a 'maybe' zone in which the user might use overdrive: and a 'yes' zone in which 'overdrive' would always be used. The 'maybe' zone had questionable benrfit in terms of time savings and greater errors. The 'yes' zone had significant tirne savings in the order of 4MO%which can translate into several seconds. With the first method. this zone began afier the fifih or sixth item (depending on overdrive speed). With the second mcthod. this zone began later after the eighth or ninth item that can be attnbutrd to the state of tension over toggling the overdrive on and off. In both cases overdrive was initiated almost irnmrdiately and maintained as long as possible before releasing to retum to the reçular scan interval to select the target. Although an overdrive hnction has the potential for significant time savings it is only usehl when the dimension of the scanned items lies in the 'yes' zone and if the user has the physical ability to use it. Genrrally, overdrive is not useful while moving across text objects. Only when scanning across many words in a line is the advantage of overdnve obvious, although words could be scanned by groups of several words and overdrive would not be used at all. However there are circumstances in which it is faster to scan with overdrive across many items than to scan by groups. Overdrive has potential benefit when targeting items near the end of a larger group. and little or no benefit when targeting items at the start of a group. 7 Task Transparent Scanning Design Guidelines 7.1 Introduction A set of guidelines is presented here as a starting point for appl ying task-transparent scanning throughout GUIS. These reflect knowledge gained through this research. Some of these guidelines are based on observations, some are based on logical analysis and sorne are based on a synthrsis of both. They will be irnproved as experience is gained. In some cases. fùnher rescarch and drvelopment is suggested where the evaluations indicated the need for a specifk guideline. but insufficient knowledge was available to suggest a guideline with confidence. 7.2 First Steps Pnor to descnbing the guidelines. it is important to drfine some of the initial steps that are associated with applying task-transparent scaming. The first step is to identiw and describe the tasks in terms of what the user wants to accomplish with certain objects and operations. This follows from the definition of task transparency. Descriptions should be indeprndent of how they are done with a mouse or keyboard. The second step is to identifi the task as either a movement task or selection task. In some cases this can be ambiguous. In this thesis, the tasks were described as either moving the text cursor to the desired text insertion point, or selecting the desired text insertion point. A movernent task is one in which the user moves an object through some range of values (e.g., text cursor location). A selection task involves the identification of some object (e.g.. text insertion point), then canying out an action at that object location (e.g., begin to extend a text selection). The results of the experiment suggest that the approach that maintains a consistent and expected view of the task. its objects and operations should be chosen. An attempt with Stratrg 4 to impose a mental mode1 of selecting the insertion point was not achieved because the subjrcts had a stronger mental view of moving the text cursor. In the case of a movement task, it is important to identiQ the object to be moved along with its range of values and any narural incremental steps. For example, with Strategies 2 and 3. the text cunor was identified as this object along with text movement keys which moved it narurally across the text. Whrn the task is to select an object, the selection set of logically associated objects should be identified along with any natural groupings and specific operations that act upon the objects (in trrms of keystrokes. if possible). For example. the text field was identitird with Strategy 4 as the selection set that was nanirally organized in units of paragraphs. lines. words and chancters. Text movement keys and the eshifi> key were identified as keys that could be used to block the text in natunl units. 7.3 Guidelines 7.3.1 Scanning Strategy .-lpp(i-scnnning ro the objeci (cg.. texr cwsor) i~tmovemenr rnsh such that ir scons tlzroiigh its range of.va.alrres. This can be accomplished in different manners. Stratcgies 2 and 3 applied scanning to the trxt cursor by repeating text movement keystrokes such that the cursor appeared to scan across the text through a range of parapphs. lines. words and characters. Consider a sequeilrial group scanning approach to movemerit rash ij'there are nairrral incvements of dij'ferent ske within ihe object S range. This permits the task to be completed in a single scanning operation. The evaluation demonstrated that Strategy 3 minimized key selections and select switch activations. It does not, however, offer significant time savings with respect to a strategy involving several single-level scanning movements. App-7 scanning across the set of related objects in a selection rask. Strategy 4 demonstrated this by applying scanning across the text in such a way that the final selection in the scaming was the target insertion point. This can be achieved by item scaming if the srlection set is small. otherwisr a sequential group scanning approach should be considered using any naturd groupings of objects. This permits the task to be cornpleted in a single scanning operation. The evaiuation demonstrated that Strategy 4 minimized physical demands of the user. but unique mors arose that detracted from potential time swings. 7.3.2 lmplementing Task Scanning 1. Begin scanning (niovin@ objects at their initial [ocarion. This guideline is an assumption based on minirnizing the distance that the object must move. It would not make sensr to move the initial location such that the user may take additional scanning steps. 2. Stop scanning (»iot.in@ objecrs at the end oj'their range r-ather than ,ri-aparound to ille opposite md. .-l[trrnate[iq.scanning objrcts shotdd iimparound to the initial sroi-ting poiilt. The users should not be forced to scan across any items not containing the target location. Strategies 2 and 3 were implemented to stop at the end of the range because the access system was 'blind' to the actual location of the text cursor and could not reposition the text cursor to the starting location. Future research is required to determine whether wrapping back to the initial location is wonh considering if the access system could do so. 3. Begin scaruting mi-oss objects at a colisistmt location srich that scanning proceeh il1 somr Iogicaljàshion. ideab Ieji-to-ri&. top-to-bottom. Overall consistency in the use of scanning should always br maintained. Dificulties were observed with Strategy 4 because this guideline was not followed. When the target was to the right or above the starting location. the mle of selecting the target as it was highlighted did not apply. 4. Scanning shou Id it ~raparoundto the initial objecr when scann ing across o bjects. This maintains consistency with the on-screen keyboard. This was not implemented with Strategy 4 because it required communication from the application to the access system that was not possible. Future research is required to determine wherher, in the case of text scanning, it is more efficient to correct overshooting by scanning fiom the top, or by backing up. 7.3.3 On-screen keyboard Provide on-screen &board shortc~itsfor frequent ft*selected appIication objecls ( e.g ., Extend/Stop Extend, OK and Cancel buttons, or Cut, Copy and Paste cornmands). This follows common design guidelines. although future research is required to detemine tradeoffs between the inclusion of objects within the on-screen keyboard versus scanning them in-place. Experimental observations showed that the extendistop extend key was the most frequently used key in al1 of the text scaming strategies. rlssign an owscr-een kyto each possible rnovenlent that ma!. need to be ~mh-rhr conrrol O/. the ILS~I: rtith the option to remove some keys as experience is gained. Although this increases cornp!exity and on-screen scanning steps. it follows from common design principles that the user should maintain control wherever possible. The results of the experiment demonstrated that most keys were used. although usage vaned with stratrgies. With an approach such as Strategy 4. however. it is possible to reduce the starting key to a single kcy. such as the cparagraph> key and still select any point. Proiide addirioilol kqsjor single-srep movernenr. Subjects using al1 of the trxt scanning stratesies experiencsd difficulty with scaming when only a single strp was required. There remained an expsctation for single step-key actions bccause of past experiencr. The prrdictive models also demonstrate that a single step-key requires fewrr switch activations than the proposed text sca~ingstrategies. -4rrange on-snwn kevs nccording to frequencv-O/-use. Predictive analysis demons trates that arranging keys according to fiequency-of-use reduces overall task time. In particular, time can be reduced the most with Strategies 3 and 4 because fewer keys are used and these can be placed for quick selection. 7.3.4 Scan Interval Retain the same scan interval in the task area as in the on-screen @board, brir consider adjusring ir separatek: The experiment indicated no particular difficulties in maintaining a consistent scan interval. Common guidelines suggest that consistency is important in maintaining the rhythm of scaming. It was not possible. however, to observe timing problems that have been anecdotally reported when wraparounds occur when scanning small groups. Scaming may be perceived as faster in such cases because of the signiticant attention shift that occurs with wrapping. Future research is required to substantiate whether a consistent scan interval is appropriate or not whrn scanning wraparounds are permittcd. 7.3.5 Time Delays 1. Provide an adjnsrahle rime deiay ai the siart oj'at~j.scanning opet-arion to ailoii the rrser ro adj~rsthis/het- ntre~irion and to pian foi- upcoming sivitch activations. Al1 strategies require this delay because of the unique planning required with every task. Observations indicated that this was different from a recovery delay used when scanning levels change (e-g.. line to word). The able-bodird subjects required this delay. but not the recovery dclay. 7.3.6 Canceling 1 . PI-oiidea mechnnism /or the user to cancel a scannitzg iask. This rnay be accomplished wi th a separate switch or by escaping after a certain number of cycles of scanning at one level if the access system is capable of sensing the cycles. Canceling provides consistency between scanning the on-screen keyboard and the task area. With Strategy 3 canceling was found to help users deal with any situation in which they were confused or needed relief. 2. Scanning should remni to the on-screen keyboard ajier canceling. This guideline follows design logic where the user should retain control over the next action which may or may not be a task scaming operation. Al1 scanning strategies were implemented following this guideline with no observable difficulties. 3. Cunceling actions should he consisient in ail siitrntions -immediaie(i* stop scannirig and restore rhe &stem Smte if'anr rrnusrral srnte (e-g.. 7.3.7 Error Correction I. Consider a simple et-ror cor-reciion of'single level bacht,ard scanning ij'the targrt locaiion is owrshot. Subjscts using Strategies 3 and 4 found it difficult to use the sequential backward/fonvard scanning error correct ion schemr. Instead. the sirnpler approach of Strategy 2 was much easier as it only used one backward scanning increment to position the text cursor brhind the target. The user could then initiate fonvard scanning through another kcy selection. Further resçarch is required to hilly explore other methods of error correction such as starting over from the top. 7.3.8 Feedback Proi~i&./èedbnckithrt~ the scanning objecr shifs leids (ij-mot-erhatz one) ru itidicarr rhr ne-u leid hm heeit seiected. This allows the user to prepare to stop scanning at the appropriate time. and confirms that the switch activation has been accepted. In the experiment. auditory 'beeps' were provided to accomplish this feedback. This was important with Strategy 3. because no visual cue was provided with the text cursor until it moved. Provide-fiedback thar indicares the level an object (or increment size) is scanning. This enables the user to determine whether to let scanning proceed, to choose the next level. or to stop scanning. In the expenment, only Strategy 4 provided such feedback. Subjects using Strategy 3 commented that the lack of visual feedback increased difficulty, as they had to mentally keep track of the levels. 7.3.9 StartingJStopping Scanning Begin task scanning with a key selecrion within the on-screen &board. This is the only option available to the user who spends most tirne within the on-screen keyboard. Task specific scaming krys allow the user control over tasks. Select switch acrii.ariorts shotrld be rrsed to select scanning levels and ohjecrs in the tnsk ai-ra. This ensures consistency with the on-screen keyboard. Al1 scaming strategies were implemented following this guideline with no observable difficulties. Resrrrne scarmirig iri the on-screeiz &board afier an object is selecred or positionrd This allows the user to choosr an action to employ on the seiected object. to choose anothcr task scanning operation. or to perform some other task. Ail scanning strategies were implemented following this guidelins with no obsemable difficulties. Conclusions 8.1 Evaluation Conclusions This research explored a new view of transparent computer access for people who use switch- based scaming systems within a graphical user interface (GUI). Rather than conventional mouse rmulation through a sca~ingscreen pointer, it was proposed to apply scanning to the underlying task and data that are the targets of the user's intentions. This is called task transpareitq*.The work reponed here dernonstrates the application of this concept to selecting text. The results provide valuable directions towards the design of scanning access systerns that enablr users to not just achieve equal access. but to achieve equal productivity. Thres new straregies for positioning the insertion point by text scanning were rvaluated throush predictivr analyses and rxperïmentation. They were compared with each othrr and wirh a standard keystrokt stratqy. Additional knowledgr of user strategies. short-term learning. mors. and perceptions was gained through the experimentation. All stntqies were implementsd in an on-scrern kryboard. WiViK. modified for this research. This cvaluation demonstrated the relative merits of the strategies with able-bodird subjects. The structure. design. and view of the text selection task for each scanning strategy created different user demands that induced distinct performances. The proposed strategies offered significant improvements in reducing key selections and switch activations by scanning across the text. One of the drawbacks associated with scanning is that, in some circumstances, the user must wait as scanning proceeds across many items. An enhancement that can be applied to al1 of the text scanning strategies to reduce this scanning time. called overdrive scanning, was evaluated in a second experirnent. Overdrive scaming allowed the subjects to control a faster scanning rate through the use of a second switch. A clear tradeoff was observed between target distance and whrther overdnve was used and offered time savings. The end result is that overdrive scanning is only usefil when targeting an item near the end of a large group and if the user has the ability to control a second switch. It is recognized that the participation of able-bodied subjects in the experiments rnay undemine the extrapolation of results to any specific population of people with disabilities. The individual motor, cognitive. and visual-perceptual abilities and their limitations due to disabiliry. may have as much influence on the effectiveness of any scanning strategy as its optimally used merits or disadvantages. When the results of both rvaluations are considered, it appears that viable stratrgirs can br designed that apply task-transparent scanning that offer fûnctionality, reduced demands. and faster interaction leading towards greater productivity. Specific limitations and probiems associated with these strategies have been identified that can now be addressed through funhrr study and desip. Design guidelines ansing from the evaluations were proposed in Chapter 7. 8.2 Suggested Extensions to other GUI Tasks Task transparent scanning can be readily applied to other tasks involving GUI objects. Specific examples of such extensions are provided in Appendiv K. As with text. the keyboard channcl can be used to achirve scanning across objrcts or directly engage them in the scanning. If keystrokes are not available, the on-screen keyboard may inject system messages but access is limited if the underlying input propenies of the GUI objects are unknown. It is possible to query the objects but this requires communication between the access system and the application. Industry is now designing operating system technology to support such interactions. " " ActiveX Accessibility. Microsoft Corporation. Redmond. WA 8.3 lnsights Gained From This Research The pnmary insight gained through this research arose fiom the realization that a scaming screen pointer provides functional transparency to the user interface of the operating system and application, but it is precisely that interface that prevents scaming users fiom being productive. A mouse action to accomplish some functional task cm become a time and effort-consuming task in itself for someone who scans. At that point. the -directnrss' of pointing which benefits able-bodied users is lost. A related insight was that direct manipulation can still benefit usrn with disabilities within a GUI rven whsn a mouse is not used. The key lies in the semantic and aniculatory properties of the interface to achieve directness. A subsequent insight was that al1 GUI objects that represent tasks and data could form different selection sets and mcrgr with the access system. Although some of these objects might fit within an on-screen kryboard. many objcct classes. e.g., trxt. have too many elemrnts to fit and/or their natural organization would be lost. It was then logical to apply scanning across specific application objccts in-place and involve those objects directly in desired tasks. The tinding that a less sophisticated scaming strategy afforded equal or better time performance than a more sophisticated strategy contnbuted the insight that the degree to which the user retained control ovsr scanning events was an important determinant of time. In order to reduce effort dsvoted to ofien rrpeated actions and typical movement patterns. user control can be replicatsd through programmed strategies. While tremendously beneficial to a user with a disability. thesr reductions corne at a time cost. However, it is difficult to improve upon programmed sequenccs because only the user knows the end target. The observed relationship between user control and timing leads to the insight that improvements might be achieved by returning some control to the user. A parallel insight was that the time spent scanning at a fixed scan interval pt-ior to reaching the target might be considered 'wasted.' The combination of these two ideas led to the evaluation of a scanning concept called overdrive scanning. While overdrive is promising in reducing time spent scanning to distant targets, its usefiilness tums out to be limited, 8.4 Suggested Future Research and Development A comparison with scanning screen pointers should be done to fùrther substantiate whether the task transparent scanning approach offers greater benefits than mouse emulation. While predictive modeis similar to those presented in this thesis can be employed. experiments must also bs conducted with users to consider the interaction issues such as those considered here. In particular. a comparison is required across a full-range of tasks to determine the impact of both approaches on overall productivity. Some of the strategies employed in the text scanning can be applied to a scanning screen pointer and should be studied. It is recognized that there are some instances in which a scaming screen pointer is the only way in which the user can achievr accrss. For examplc. there are applications designed exclusively for pointing input that do not include any keystroke equivalencies to tasks nor provide access to underl ying oprrating system messages. In some of these cases. pointing is the primary task and a scaming screen pointer is appropriate. In other cases. it is a matter of providing access to a poorly designrd application. Dnmatically improving overall time performance (speed) remains an elusive goal for the text selection task. Future research is required to determine whether substantial rare improvements are attainable. There are a number of areas in which improvements may be found. Throughout any resrarch involving thesc areas, it is important to considrr the drgree to which the user retains control and the demands that are placed on the user. One improvement to consider is to link the four sub-tasks of srlrction together into one scanning operation (select. extend. select. and stop rxtend) or into two opentions (select, extend -select. stop extend). This minimizes any on- screen scanning. However, methods to ensure accuracy must be studied so that any gains are not offset by time Iost to correction of errors. These methods include various forrns of ferdback; adjustments to the scan interval to allow for planning during the scaming process: and canceling and error recovery procedures. Feedback issues that require study include notification to the user as to which level is about to be scanned. This also impacts other tasks involving the direct engagement of a GUI object in scanning. Although the scaming text approach of Strategy 4 addresses this issue, it is dificult or inappropriate to apply to other tasks such as scrolling, resizing or moving windows, and button srlection. Various forms of auditory feedback should be considered. but with caution so that the user is not burdened with excess sensory feedback. Attention rnust not be drawn away from the task any more than necessary. If the sca~ingobject, such as the text cursor. is not visually distinct. it rnay be necessary to augment it so that tracking is facilitated. Methods should be studied to determine appropriate drlays. afier a change of scanning lrvel to account for the attention shifi and planning that occurs in addition to the physical recovery. These are individual factors that va- among individuals and rnay Vary among different levels of scanning. The possibility exists for some trade-off between necessary time delays after a scanning level change, and the particular level. For example. adjusting from pangraph to linr scanning rnay take longer than word to character scanning because the visual differencr is greater. Canceling procedures must be examined closely if the text selection subtasks are linked to ensure that the user can recover fiom an undesired action. such as an unwanted text selection. without negative consequences. The user should also be able to recover fiom an error without having to stan over from the beginning, although that should remain an option. Canceling while the trxt is being highliçhted is a panicuiar concem becauss the user rnay want to leave the text highlightrd and continue with anothrr operation to extend or act upon that selection. Or. the user rnay want to perform some other operation that rnay rnistakenly delete that selrcted trxt if the highlight is not automatically removed. This represents a typical tradeoff with sca~ing- should the scanning system reduce effort while reducing user control. or should the user remain in control at the cost of çreater effort? The tradeoff betwcrn user control and prograrnrned strategies should be studied in greater detail. This would facilitate decision-making by users and designers of access technologies. For every pre-propmmed feature that is incorporated in a scanning system, questions are raised as to whether or not the benefit outweighs the loss of control, and the potential loss of time in some circumstances. Additional effort rnay be required in the ''unusual" circumstances that don't apply to the pre-programmed scenario. One atypical occurrence rnay undo any gains made with the pre- pr~~mrnrnedstrategirs. For example. dealing with overshooting errors with the scanning text strateg studied here was difficult and time consuming. Dealing with thesr uncommon tasks and error correction within the GUI is a crucial area of research. In this research I demonstrated a minimizing of the physical demands through the application of scanning to the text selection task. The application of scanning to othcr tasks also minimizes physical demands. However. there rnay in fact be minimal improvements that are possible to reduce the task tirne given the limiting nature of single and dual switch automatic scaming. If this is the case. schemes that minimize planning associated with tasks that are not pre-programmed and faci litate error correction may improve productivi ty. Sensing the text to reduce the scanning steps across a large group may be possible. but it remains difficult to predict the intentions of the user. Thus. it is questionable whether such sensing adds value. Sensing of othrr GUI controls is more likely to result in productivity gains. For example. detrmjning the extent of menus and the existence of submenus would greatly rase menu scanning. Similarly. detemining the types of control in a dialog box and appropriate user rrsponses is feasiblr and would rrduce additional on-screen keyboard sca~ing. The fixed nature of the scaming interval remains problematic. While overdrive scanning can address this issue. it is not always feasible. Other mrans to quickly jump across a large proup so as to collapse several scan intervals should be considrred. Multi-modal access or mixed mode should be investigated funher. The inclusion of some direct control, even if limited or imprecise. may make a significant difference. Methods by which the user control has control over the scan interval should be studied. It is recognized that step scaming is the most common method of providing such control. However, it is important to consider the physical effort and repetitions that anse. A short-tenn gain in control may result in long-terni problems in the health of the user, e.g.. due to the possibility of repetitive strain injury. The impact of switch activations on the fatigue level of the user and its potential for repetitive strain injury is a crucial area of research. This is an issue for al1 scanning users. As scanning systems are designed for increased productivity and function, expectations by the user and by others to use the computer for longer prnods of time will increase. Althouçh solutions such as those described in this thesis may reduce the number of switch activations within certain tasks. this may induce the user to wmk longer. Switch activations can easily number in the thousands in one work period. With only one or two switch inputs using consistent physical actions. the possibili ty for repetiiivr injuries is high. Therefore. research must continue on multiple modes of input such that reprtition with any one mode is minimized. One aspect of scan interval that was not addressed here was whethther it should Vary according to the goup size. This is a concem when scaming wraps around a group. In extrnding scanning across non-text GUI objects such as dialog controls and menus. a potential problem arises when scanning wnps around a small group because it happens more quickly and creates a distracting attention shifi. It is suggested that a sludy be conducted to determine whethrr rht: scan interval should be adjusted by some factor according to the group size. A fixed scan interval may bc appropriate above some size. but below that size the scan interval rnay need to be Irngthrned. Another recognized limitation of this research that should be considered in future work is rvaluation with end-usen who have disabilities. It is important to drtermine the impact of individual di fferencrs that influence the usability of the proposed scanning approaches. In panicular. issues of cognitive level. spatial planning abiiity. and prior experience will likrly have an impact on usability. Physical ability should have less of an impact because switches are identified and irnplrmented in such a way that their use is nearly indistinguishable from able- bodied users. Howrvctr. random mors will more likely be introduced. This furthrr corroborates the nred to ensure appropriate error-recovery schrmes. 8.5 Contributions The most important contribution of this research within the context of computer accessibility is a new interpretation of transparent access. An approach of task transpai-ency allows the user to directly access the underlying tasks and data without requiring that user to perform equivalent iünctions to the standard input devices. This opens the way for Future access systems to be designed that are more appropriate to the abilities of the user rather than force the user to adapt to emulating functions that are beyond their ability. In particuiar, this approach has a great impact on scaming access to tasks in a GUI that normally require mouse or extensive keyboard input. In the case of selecting text. directness to the task can be achieved by applying scaming within the text area itself. An immediate advantage is minimal physical demands. It was demonstrated that any point in the text can be reached in a single scaming operation (one on-screen keyboard selection) using at lrast three but no more than six switch activations. The concepts are readily extended across GUI screen objects includins menus. dialog buttons and fields. and window controls. Through the use of such strategies. users can signiticantly reducr their efforts. and in doing so, achieve pater overall productivity and accompl ish tasks that are otherwise strenuous. Additional contributions are related to specific objectives: Objective 1: To &iiw and pmrohpr srrategies rhat appii. stritch-based scanning iiithin a rrw fieki ro sekr rrirr. 1 demonstrated that GUI objects can be incorporated as selection sets within the access system such that they are acted upon or srlected directly without intermediate pointing actions. In some cases. thesr objects retain their location while others are brought into the on-screen keyboard. When objects. such as trxt. are lefi in-place. their natural structure and arrangement can be used to advantage by the access system. In accessing these objects by sca~ing1 have proposed two approaches. One approach involves moving the GUI object, if it has such movement properties. in a scanning fashion. The other approach involves scaming across objects to select a desired object. In the case of selecting text, both approaches are feasible. These approaches have been implemented within the WiViK on-screen keyboard by the author. Additional designed modifications to WiViK were camed out to allow scanning through repeating keystrokes. On-screen keyboard layouts for each of the strategies evaluated were designed and programmed. It has been demonstrated that the keyboard chamel is a practical information camer to extend scaming access outside of the on-screen keyboard to the text. Similar scanning approaches could be irnplemented with any access systrm that has a keyboard smulating interface (KEI) and the ability to repeat keys in a controllable fashion. However. 1 have identified that access systerns may require the ability to query applications to acquire information about GUI object properties as well as inject system messages when keyboard input is not feasible and mouse emulation impractical. This substantiates suggestions by others that an additional two-way information channel is needed other than the keyboard and mouse input. Objective 2: To derelop the necessaq?nierhods and tools to ei-ahrare the proronpe straregia and oi?euiiri\vscartning merhods. both aaa&icalf~*and rxper-imental(i: Two test applications have been drveloped that have usetllness outside of this specific research. Thrse applications have been designed for genenl evaluation purposes such that any accrss scheme may be used. They include data collection features that monitor user performance. although it is recognized that such data collection rnay need to be modified for other studies. Along with the test applications I developed a series of models that can be used to predict performance with additional GUI scaming tasks. Intemal references to text units in the models can be replaced with other units appropriate to the task. These are useful to predict performance measures in error-free conditions. Objective 3: To eiolrrnrr rhe eficriveiiess and re1arit.e nterits of ench protocpe srrateg??in tel-lm of'dernands on the ~tsrr.and uesirlrirg user pr~orrnances. 1 demonstrated the effectiveness of the standard keystrokes strategy and three text scaming strategies using predictions of error-free performance and expenmental observations. Al1 text scanning strategies were shown to be faster and less physically dernanding that the standard keystroke strategy. The scanning text keys strategy significantly reduced the number of key selections and switch activations. It was easy to use and subjects had control over al1 text cursor movements. Time was reduced by approximately one-fifih. The sequential scanning text keys strategy further reduced physical demands. Planning and attention switching between the text area and on-screen keyboard were minimized. Time savings were, however, equivalent to the repeating keystrokes strategy. The text scanning strategy had similar effkiencies as the previous strategy. While this strategy was easy to use, its time performance was less than expected and its style did not match the usen' expectation of controlling the text cursor. No one strategy is 'best.' The costs associated with specific attention requirements. error correction. and inefficient scanning sequences suggest that further work is required to refine the strategies. The evaluation of overdrive scanning provides knowledge of a scanning concept that has been implemented but never evaluated in such detail. This evaluation demonstrated the usefulness of overdrive in certain circumstances where a scanning goes past a certain number of items. In these circumstances. a high degree of physical ability is required to gain benefit. It was shown to have no advantage for general scanning of arrays containing only several items in a scan _moup. The identi fied problem of 'wasted' scanning time remains unresolved. Objective 4: To srrggesr desig~iguidelines and scanning characteiisrics that considu the ei*aZzrariivinji>/-niarioil regarding trser- demands and pej$wniances. Design guidelines for scanning in a task transparent fashion have bern formulated. Although hrther work is required. these provide a foundation to build upon as further expenence is gained. An access system developer can use this foundation to extend the concepts in new ways with scaming and other access methods. Finally. I have suggested future areas of research that may improve overall productivity. Arras of concem that require attention are identified. There remains much work to be done to ensure users with severe physical limitations can fully enjoy effective access to cornputers. This thesis has contributed new knowledge towards improving such access and has demonstrated the feasibility for a new task transparent approach by which further gains are possible. 8.6 Final Words This thesis advancrs the state-of-the-art of computrr access for people with physical disabiliries. A new view of transparent access is offered that can be applied towards the design of accrss systems that enable users to not just achieve functional access. but to achieve effective accrss. In particular. people who use switch-based scaming access methods will benrfit from this approach. Physical drmands can be reduced and directness of access to the tasks that the user wants to accomplish can be improved. 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Application software design guidelines: Increasing the accessibility of application software to people with disabilities and older usen. Trace Research and Development Center? Madison WI. Appendix A WiViK Keyboard Definitions: Evaluation 1 Strategy 1 : Standard Keystrokes 2, 1, ICON, "LftChar", Macro, " 3. 1, S.mol, 'Kg, Macro, " 4. 1, ICON, "StopExtendW,Macro, " L, 1, ICOEI, "3tChar". Macro. " 2, 1, ICOEI, "LitChar", Macro, " 4, 1, :COPI. "Extend", Macro. ".r?AGE(?)> 1, 1. ICCN, *3tCharw, Wacro, " 3, 1, S;mSal, 'KI, Wacro, " 3, 1, ICON, *lStopExtend",Macro, " ,* WiViK 8 Keyboarà Definition File -1 , - Scan3. KSM - : IDef inrtionI CapsLock4ct ian=Toqq1eOf if T:ipe=Macrc, ROWS= 4, Cols= 4, Paqes= 7, ~con~ib=wivicon.d?l: [EndDei inicionl 3, 7, S:mboL, *Kt,Slacro, w 4, 1, ICOPI, "Extend", Macro, w -1, 1, ICON, wStopExtsnd", Macro. w ;-Wi'JiK 8 Keyboard Definition File */ - C 1995 The Huqh MacMillan Rehabrlitation Centre * Scan4 .KBM - ,' IDef Fni tionl ~aps~ackAction=ToqqLeOff, T:qe=Macro. aows= 4, COLS= 4, Pages= 3, iconlib=wi~::con.dll; [BnàDefinitionl 3. 1, S:mbcl, 'Kt, Macro. " 4, 1, ICOPT, "Extend", Macro, " Pattern image pp ---- 1 Beg.: 3, 1, 5, 5, End: 3,4,3,4 (Para, line, word, char) Beg.: 2, 3, 5, 1, End: 5, 1,6,2 (Para, line, word, char) . Egg - :. ": :,: '.,A,*Ll+.--. "'- - .II '. ., . . l~~~~~~~'-~~w zrcc u rr@7-=czl---n-- 3 rrrn ffiCu*fi.lr Jiii-i.rri3ZI33-n ZJZ B rrrrr~z ZEE -m rri - 1 Beg.: 1.3. 6. 1. 1 End: 4.3, 1.3 1 (Para. line. word. char) Beg.: 1. 2. 7. 1. End: 4. 3. Il, 5 ( Para, 1ine, word. char) Beg.: 1. 5. 9. 1. End: 3, 4. 1, 3 (Para, line. word, char) 24 Beg.: 1. 1. 5.6. End: 4. 3. 8.3 (Para, line, word. char) 25 Beg.: 2, 2. 1. 2. End: 3. 1, 5. 3 (Para, line. word, char) Appendix C Predicted Movements and Times: Evaluation 1 .Table C-la: Conservative predicted movement steps and total time for Strategy 7 :Beginning Point 7 Trial dnP dn rtW rt lt Itw Extd Beg. Time 1 2 O 4 4 O O 1 38.1 2 1 2 3 O O O 1 30.2 3 1 O O O O O 1 10.9 4 f O 7 6 O O 1 47.0 5 O 1 O O O O 1 9.9 6 1 2 O O O 2 1 29.7 7 1 3 7 1 O O 1 50.5 8 O 2 4 2 O O 1 32.2 9 1 2 5 1 O O 1 39.1 10 O 1 6 1 O O 1 32.7 11 2 O 7 O O O 1 40.6 12 O 1 9 4 O O 1 49.0 13 1 3 4 5 O O 1 48.0 14 1 1 4 3 O O 1 35.1 15 O 2 3 O O O 1 24.8 16 1 4 O O O 2 1 38.6 17 1 1 10 2 O O 1 54.0 18 2 1 9 3 O O 1 57.9 19 O 2 7 O O O 1 38.6 20 1 2 O O O 1 1 24.8 21 O 2 5 O O O 1 31.7 22 O 1 6 O O O 1 30.7 23 O 4 8 O O O 1 51.O 24 O O 4 5 O O 1 29.2 25 1 1 O O 2 1 1 27.2 AVG 0.72 1.52 4.48 1.48 0.08 0.24 1 36.1 Table C-16: Conservative predicted movement steps and total time for Strategy 1: End Point 2 Trial dnP dn rtW rt It Itw Stop End Total 1 1 O O O O O 1 10.9 49.0 2 3 1 O O 5 2 1 53.5 03.7 3 1 2 O O 4 O 1 33.7 44.6 4 2 2 O O 4 1 1 44.1 91.1 5 2 O O O 5 O 1 33.7 43.6 6 3 2 O O 7 3 1 69.8 99.5 7 2 3 O O 1 7 1 67.8 1 18.3 8 2 O O O O O 1 16.3 48.5 9 2 5 O 4 O O 1 46.5 85.6 10 O 2 2 1 O O 1 23.3 55.9 II 1 3 4 2 O O 1 42.1 82.7 12 2 3 O O 1 4 1 53.0 102.0 13 O 4 O O 2 O 1 30.2 78.2 14 2 3 O O 7 O 1 54.0 89.1 15 3 1 2 2 O O 1 37.1 61.9 16 2 O O O O O 1 16.3 54.9 17 2 3 5 8 O O 1 62.9 116.8 18 3 1 O O 1 1 1 34.7 92.6 19 O 4 O O 1 O 1 26.7 65.3 20 2 O O 3 O O 1 22.3 47.0 21 4 O O O 3 4 1 57.4 89.1 22 3 3 5 5 O O 1 62.4 93.1 23 3 O O O 6 5 1 67.3 1 18.3 24 3 3 5 3 O O 1 58.4 87.6 25 2 1 4 3 O O 1 40.6 67.8 AVG 2 1.84 1 .O8 1.24 1.88 1 .O8 1 42.6 78.6 Table C-2a: Optimal predicted rnovement steps and total tirne for Strategy 1: Beginning Point 1 Trial dnP dn rtW rt It Itw Up end hme pDn Ext Beg. 1 2 O 4 4 O O O O O O 1 34.2 2 1 2 3 O O O O O O O 1 30.2 3 1 O O O O O O O O O 1 10.9 4 1 O O O 3 1 O 1 O O 1 30.7 5 O 1 O O O O O O O O 1 9.9 6 1 2 O O O O O O 1 O 1 25.7 7 2 1 4 1 O O 1 O 0 0 1 41 -6 8 O 2 3 O 1 O O O O O 1 28.2 9 1 2 4 1 O O O O O O 1 34.7 10 O 1 5 1 O O O O O O 1 28.2 11 2 O O O O 4 O 1 O O 1 40.6 12 O 1 O O 3 1 O 1 O O 1 29.7 13 1 3 4 2 O O O O O O 1 40.1 14 1 1 5 O 1 O O O O O 1 36.1 15 1 O O O O 1 O O O O 1 15.8 16 2 O O O 1 O O O 1 O 1 25.7 17 1 1 O O O 1 O 1 O O 1 24.8 18 2 1 O O 3 O O 1 O O 1 35.6 19 O 2 O O O 2 O 1 O O 1 28.7 20 1 2 O O O 1 O O O O 1 24.8 21 O 2 5 O O O O O O O 1 31.7 22 O 1 O O O 4 O 1 O O 1 34.2 23 1 O 3 O 1 O 1 O O O 1 30.7 24 O O 5 4 O O O O O O 1 26.7 25 1 1 O 1 O O O O 1 O 1 22.3 Avg 0.88 1.04 1.80 0.56 0.52 0.60 0.08 0.28 0.12 0.00 1.00 28.9 Table C-2b: Optimal predicted movement steps and total time for Strategy 1: End Point 2 Trial dnP dn rtW rt ' R Itw Up end hom pDn Stop End Tot 1 1 O O O O O O O O O 1 10.9 2 3 1 O 2 O 3 O O O O 1 43.1 3 1 2 O O O 1 O O O O 1 24.8 4 2 2 O 1 O 2 O O O O 1 36.1 5 2 O O 5 O 1 O O O O 1 26.2 6 O O 2 2 O O 2 O O t 1 33.2 7 O O O 3 O O 2 O 1 1 1 33.2 8 2 O O O O O O O O O 1 16.3 9 O O O 4 O O 1 O O 1 1 22.3 10 O 2 2 1 O O O O O O 1 22.3 11 1 3 O O O O O 1 O O 1 28.7 12 3 O O O O O 1 O O O 1 27.7 13 O 4 O O 2 O O O O O 1 30.2 14 3 O O 1 O 1 1 O O O 1 33.7 15 3 1 2 2 O O O O O O 1 35.1 16 2 O O O O O O O O O 1 16.3 17 3 O O 2 O O 2 O O O 1 35.6 18 O O O O 1 1 2 O O 1 1 32.7 19 O 4 O O 1 O O O O O 1 26.7 20 2 1 O 1 O O O O O O 1 21.8 21 4 O O 2 O O O O 1 O 1 35.1 22 4 O 1 5 O O 1 O O O 1 41.6 23 3 O O 2 O O O O 1 O 1 29.7 24 4 O O 1 O O 2 O O O 1 40.1 25 2 O 5 3 O O O O O O 1 36.6 Avg 1.80 0.80 0.48 1.48 0.16 0.36 0.56 0.04 0.12 0.16 1.00 29.6 Table C-3a: Conservative predicted movement steps and total time for Strategy 2: Beginning Point 1 Trial dnP dn rtW rt It Itw Ext OSK Text Beg Tirne Time Time 1 2 O 4 4 O O 1 16.3 lt .4 27.7 2 1 2 3 O O O 1 18.8 6.9 25.7 3 1 O O O O O 1 10.9 1 .O 11.9 4 1 O 7 6 O O t 16.3 14.9 31.2 5 O 1 O O O O 1 9.9 1 .O 10.9 6 1 2 O O O 2 1 20.3 5.9 26.2 7 1 3 7 1 O O 1 20.8 12.9 33.7 8 O 2 4 2 O O 1 15.3 9.4 24.8 9 1 2 5 1 O O 1 20.8 9.9 30.7 10 O 1 6 1 O O 1 15.3 8.4 23.8 11 2 O 7 O O O 1 14.4 9.9 24.3 12 O 1 9 4 O O 1 15.3 14.9 30.2 13 1 3 4 5 O O 1 20.8 14.4 35.1 14 1 1 4 3 O O 1 20.8 9.9 30.7 15 O 2 3 O O O 1 13.4 5.9 19.3 16 1 4 O O O 2 1 20.3 7.9 28.2 17 1 1 11 O O O 1 18.8 13.4 32.2 18 2 1 9 3 O O 1 20.8 16.3 37.1 19 O 2 7 O O O 1 13.4 9.9 23.3 20 1 2 O O O 1 1 20.3 4.5 24.8 21 O 2 5 O O O 1 13.4 7.9 21.3 22 O 1 6 O O O 1 13.4 7.4 20.8 23 O 4 8 O O O 1 13.4 12.9 26.2 24 O O 4 5 O O 1 10.9 9.9 20.8 25 1 1 O O 2 1 1 23.8 5.4 29.2 -- - -- Avg. 0.72 1.52 4.52 1.4 0.08 0.24 1 16.7 9.3 26.0 Table C-3b: Conserwative predicted rnovement steps and total tirne for Strategy 2: End Point 2 Trial dnP dn rtW rt It Itw Ext OSK Txt End Total Time Time Time Tirne 1 1 O O O O O 1 10.9 1.0 11.9 39.6 2 3 1 O O 5 2 1 23.8 12.4 36.1 61.9 3 1 2 O O 4 O 1 18.8 7.9 26.7 38.6 4 2 2 O O 4 1 1 23.8 10.4 34.2 65.3 5 2 O O O 5 O 1 14.4 7.9 22.3 33.2 6 3 2 O O 5 3 1 23.8 14.9 38.6 64.8 7 2 3 O O 1 7 1 23.8 14.4 38.1 71.8 ------8 2 O O O O O 1 10.9 2.5 13.4 38.1 9 2 5 O 4 O O 1 17.3 12.4 29.7 60.4 10 O 2 2 1 O O 1 15.3 5.9 21.3 45.0 11 1 3 4 2 O O 1 20.8 11.4 32.2 56.4 12 2 3 O O 1 4 1 23.8 11.4 35.1 65.3 13 O 4 O O 2 O 1 13.4 6.9 20.3 55.4 14 2 3 O O 7 O 1 18.8 13.4 32.2 62.9 15 3 1 2 2 O O 1 20.8 9.4 30.2 49.5 16 2 O O O O O 1 10.9 2.5 13.4 41.6 17 2 3 5 8 O O 1 20.8 19.8 40.6 72.8 18 3 1 O O 1 1 1 23.8 6.4 30.2 67.3 19 O 4 O O 1 O 1 13.4 5.4 18.8 42.1 20 2 O O 3 O O 1 12.9 5.9 18.8 43.6 21 4 O O O 4 3 1 19.3 12.4 31.7 53.0 22 3 3 5 5 O O 1 20.8 17.8 38.6 59.4 23 3 O O O 6 5 1 19.3 15.3 34.7 60.9 24 3 3 5 3 O O 1 20.8 15.8 36.6 57.4 25 2 1 4 3 O O 1 20.8 11.4 32.2 61.4 Avg . 2 1.84 1.08 1.24 1.84 1.04 1 18.5 10.2 28.7 54.7 Table C-4a: Optimal predicted movement steps and total time for Strategy 2: Beginning Point 1 Triai dnP dn rtW rt It Itw Up end home Ext OSK Text Beg 1 2 O 4 4 O O O O O 1 16.3 11.4 27.7 2 1 O O O O 7 O O O 1 15.8 8.4 24.3 3 1 O O O O O O O O 1 10.9 1.0 11.9 4 1 O 7 6 O O O O O 1 16.3 14.9 31.2 5 O 1 O O O O O O O 1 9.9 1.0 10.9 6 O 5 O O O O O O O 1 9.9 5.4 15.3 7 2 O O 1 O 7 O O O 1 17.8 10.9 28.7 8 O 2 4 2 O O O O O 1 15.3 9.4 24.8 9 2 O O 1 O 5 O O O 1 17.8 8.9 26.7 10 O 1 6 1 O O O O O 1 15.3 8.4 23.8 11 2 O 7 O O O O O O 1 14.4 9.9 24.3 12 O 1 9 4 O O O O O 1 15.3 14.9 30.2 13 1 3 4 5 O O O O O 1 20.8 14.4 35.1 14 O 4 5 3 O O O O O 1 15.3 13.4 28.7 15 1 O O O O 1 O O O 1 15.8 2.0 17.8 16 O 9 O O O O O O O 1 9.9 9.4 19.3 17 2 O O O O 6 O O O 1 15.8 8.9 24.8 18 2 1 O O 4 O O 1 O 1 23.3 7.9 31.2 19 O 2 7 O O O O O O 1 13.4 9.9 23.3 20 O 5 O O O O O O O 1 9.9 5.4 15.3 2 1 O 2 5 O O O O O O 1 13.4 7.9 21.3 22 O 1 6 O O O O O O 1 13.4 7.4 20.8 23 1 O O O O 9 O O O 1 15.8 10.4 26.2 24 O O 4 5 O O O O O 1 10.9 9.9 20.8 25 O 6 O 1 O O O O O 1 11.9 7.4 19.3 Avg 0.72 1.72 2.72 1.32 0.16 1.4 O 0.04 O 1 14.6 8.8 23.3 Table C4b: Optimal predicted movement steps and total time for Strategy 2: End Point 2 Trial dnP dn rtW rt It Itw Up end hme Stop OSK Text End Tot 1 1 O O O O O O O O 1 10.9 1.0 11.9 39.6 2 3 O 6 2 O O O O O 1 16.3 12.4 28.7 53.0 3 1 2 O O 4 O O O O 1 18.8 7.9 26.7 38.6 4 2 2 O 1 O 2 O O O 1 22.3 8.4 30-7 61-9 5 2 O O O 5 O O O O 1 14.4 7.9 22.3 33.2 6 2 1 4 1 O O O O O 1 20.8 8.9 29.7 45.0 7 2 2 3 O 1 O O O O 1 22.3 9.4 31.7 60.4 8 2 O O O O O O O O 1 10.9 2.5 13.4 38.1 9 3 O 5 5 O O O O O 1 16.3 14.4 30.7 57.4 10 O 2 2 1 O O O O O 1 15.3 5.9 21.3 45.0 11 O 6 O O O O O 1 O 1 14.4 6.4 20.8 45.0 12 3 O O O O O 1 O O 1 16.8 4.5 21.3 51.5 13 O 4 O O 2 O O O O 1 13-4 6.9 20.3 55.4 t4 3 O O 1 O 1 1 O O 1 23.8 6.4 30.2 58.9 15 3 O 5 2 O O O O O 1 16.3 11.4 27.7 45.5 16 2 O O O O O O O O 1 10.9 2.5 13.4 32.7 17 3 O O 2 O O 2 O O 1 18.8 8.4 27.2 52.0 18 3 1 O O 7 O O O O 1 18.8 11.9 30.7 61.9 19 O 4 O O 1 O O O O 1 13.4 5.4 18.8 42.1 20 2 O O 3 O O O O O 1 12.9 5.9 18.8 34.2 21 4 O O 2 O O O O 1 1 18.8 6.9 25.7 47.0 22 3 3 5 5 O O O O O 1 20.8 17.8 38.6 59.4 23 3 O O 2 O O O O 1 1 18.8 5.9 24.8 51 .O 24 3 O O 1 O O 2 O O 1 18.8 6.9 25.7 46.5 25 2 O 5 3 O O O O O 1 16.3 11.4 27.7 47.0 Avg 2.08 1.08 1.4 1.24 0.8 0.12 0.24 0.04 0.08 1 16.8 7.9 24.8 48.1 Table C-5.:Optimal predkted movernent steps and total time for Strategy 3: Beginning Point 1 . t Trial dnP dn rtW rt Extend OSK Text Beg. Ti me Tirne Time 1 2 1 5 5 1 10.9 14.4 25.2 2 1 3 5 1 1 10.9 10.9 21 -8 3 1 1 1 1 1 10-9 4.0 14.9 4 1 1 8 7 1 10.9 17.8 28.7 5 O 1 1 1 1 9.9 3.0 12.9 6 1 3 1 1 1 10.9 6.4 17.3 7 1 3 8 2 1 10.9 15.3 26.2 8 O 2 5 3 1 9.9 11.4 21.3 9 1 3 7 2 1 10.9 14.4 25.2 10 O 1 7 2 1 9.9 10.9 20.8 11 2 1 8 1 1 10.9 12.9 23.8 12 O 1 10 5 1 9.9 16.8 26.7 13 1 4 5 6 1 10.9 17.3 28.2 14 1 2 6 4 1 10.9 14.4 25.2 15 O 2 4 1 1 9.9 7.9 17.8 16 1 5 1 1 1 10.9 8.4 19.3 17 1 2 12 1 1 10.9 16.8 27.7 18 2 2 10 4 1 10.9 19.8 30.7 19 O 2 8 1 1 9.9 11.9 21.8 20 1 3 1 1 1 10.9 6.4 17.3 21 O 2 6 1 1 9.9 9.9 19.8 22 O 1 7 1 1 9.9 9.4 19.3 23 O 4 9 1 1 9.9 14.9 24.8 24 O O 4 6 1 8.9 10.9 19.8 25 1 2 1 2 1 10.9 6.9 17.8 Avg. 0.72 2.08 5.6 2.44 1 10.5 11.7 22.2 Table C-56: Optimal predicted movement steps and total time for Strategy 3: End Point 2 1 Trial dnP dn rtW rt Stop OSK Text End Total Time Time Time Time 1 O 3 3 5 1 9.9 12.4 22.3 47.5 2 3 2 6 3 1 10.9 15.8 26.7 48.5 3 1 3 5 6 1 10.9 16.3 27.2 42.1 4 2 3 3 2 1 10.9 11.9 22.8 51.5 5 1 5 4 6 1 10.9 17.3 28.2 41.1 6 3 3 3 3 1 10.9 13.9 24.8 42.1 7 2 4 1 5 1 10.9 13.4 24.3 50.5 8 1 5 1 8 1 10.9 15.8 26.7 48.0 9 3 2 5 6 1 10.9 17.8 28.7 54.0 10 O 2 8 2 1 9.9 13.4 23.3 44.1 11 1 4 10 3 1 10.9 19.3 30.2 54.0 12 2 4 1 4 1 10.9 12.4 23.3 50.0 13 1 4 7 3 1 10.9 16.3 27.2 55.4 14 2 4 4 2 1 10.9 13.9 24.8 50.0 15 3 2 5 3 1 10.9 14.9 25.7 43.6 .. 16 1 4 3 5 1 10.9 14.4 25.2 44.6 17 2 4 7 9 1 10.9 23.8 34.7 62.4 18 3 2 6 4 1 10.9 16.8 27.7 58.4 19 1 2 8 2 1 10.9 14.4 25.2 47.0 20 2 2 1 3 1 10.9 9.4 20.3 37.6 21 3 4 1 4 1 10.9 13.4 24.3 44.1 - - 22 3 4 11 6 1 10.9 25.7 36.6 55.9 23 2 5 1 4 1 10.9 13.4 24.3 49.0 24 3 4 8 4 1 10.9 20.8 31.7 51.5 25 2 2 5 4 1 10.9 14.9 25.7 43.6 Avg. 1.88 3.32 4.68 4.24 1 10.8 15.7 26.5 48.6 - Table C-6a: Optimal predicted movement steps and total time for Strategy 4: Beginning Point 1 Trial dnP dn rtW rt Extend OSK Text Beg. Time Time Time 1 3 1 5 5 1 10.9 15.3 26.2 2 2 3 5 1 1 10.9 12.4 23.3 3 2 1 1 1 1 10.9 5.4 16.3 4 2 1 8 7 1 10.9 19.3 30.2 5 O 2 1 1 1 9.9 4.5 14.4 6 2 3 1 1 1 10.9 7.9 18.8 , 7 2 3 8 2 1 10.9 16.8 27.7 8 O 3 5 3 1 9.9 12.4 22.3 9 2 3 7 2 1 10.9 15.8 26.7 10 O 2 7 2 1 9.9 12.4 22.3 11 3 1 8 1 1 10.9 13.9 24.8 12 O 2 1O 5 1 9.9 18.3 28.2 13 2 4 5 6 1 10.9 18.8 29.7 14 2 2 6 4 1 10.9 15.8 26.7 15 O 3 4 1 1 9.9 8.9 18.8 16 2 5 1 1 1 10.9 9.9 20.8 17 2 2 12 1 1 10.9 18.3 29.2 18 3 2 1 O 4 1 10.9 20.8 31.7 - - - - - 19 O 3 8 1 1 9.9 12.9 22.8 20 2 3 1 1 1 10.9 7.9 18.8 21 O 3 6 1 1 9.9 10.9 20.8 22 O 2 7 1 1 9.9 10.9 20.8 23 O 5 9 1 1 9.9 15.8 25.7 24 O O 5 6 1 8.9 12.4 21.3 25 2 2 1 2 1 10.9 8.4 19.3 Avg. 1.32 2.44 5.64 2.44 1 10.5 13.0 23.5 L Table C-66: Optimal predicted movernent steps and total tirne for Strategy 4: End Point 2 Trial dnP dn rtW rt Stop OSK Text End Total Time Tirne Time Time 1 O 4 3 5 1 9.9 13.4 23.3 49.5 2 4 1 6 3 1 10.9 15.3 26.2 49.5 3 2 2 5 6 1 10.9 16.8 27.7 44.1 4 3 2 3 2 1 10.9 11.9 22.8 53.0 5 2 4 4 6 1 10.9 17.8 28.7 43.1 6 4 2 3 3 1 10.9 13.9 24.8 43.6 7 3 3 1 5 1 10.9 13.4 24.3 52.0 8 2 4 1 8 1 10.9 16.3 27.2 49.5 9 4 1 5 6 1 10.9 17.3 28.2 54.9 10 O 4 8 2 1 9.9 15.3 25.2 47.5 11 2 3 10 3 1 10.9 19.8 30.7 55.4 12 3 3 1 4 1 10.9 12.4 23.3 51.5 13 2 3 7 3 1 10.9 16.8 27.7 57.4 14 3 3 4 2 1 10.9 13.9 24.8 51 .5 15 4 1 5 3 1 10.9 14.4 25.2 44.1 16 2 3 3 5 1 10.9 14.9 25.7 46.5 17 3 3 7 9 1 10.9 23.8 34.7 63.9 18 4 1 6 4 1 10.9 16.3 27.2 58.9 19 2 1 8 2 1 10.9 14.4 25.2 48.0 20 3 1 1 3 1 10.9 8.9 19.8 38.6 21 4 3 1 4 1 10.9 13.4 24.3 45.0 22 4 3 11 6 1 10.9 25.7 36.6 57.4 23 3 4 1 4 1 10.9 13.4 24.3 50.0 24 4 3 8 4 1 10.9 20.8 31.7 53.0 25 3 1 5 4 1 10.9 14.4 25.2 44.6 Avg. 2.8 2.52 4.68 4.24 1 10.8 15.8 26.6 50.1 Appendix D Subject Instructions: Evaluation 1 Common Task Instructions (All Strategies) When the tria1 begins you will be shown a document of text that cons ists of little Fey squares each representing a letter. combined to form words. lines and parapphs. A solid BLACK square represents the cursor. A GREEN square represents the start of the block to select. A RED square represents the end of the block to select. For each trial: Select the Start key to begin a trial. Move the cursor to the GREEN square using the most efficient cursor movement keys. The meen square tums PINK when the cursor is over top of it. C Select the Extend key. Move the cursor to the RED square using the most efficient cursor movement keys. The green square tums BLUE when the cursor is over top of it. Select the Stop Ertend key. Strategy 1 : Standard Keystrokes This method is similar to using a standard keyboard. Le.. selecting movement keys to move the cursor over the text. Kcys are defined within the on-screen keyboard to move the insertion point in blocks (word. paragraph. home. end. page up and page down). You select the nrcessary movrment keys as many times as are necessary to move the cuwor. Repeating keys are not aclailable. El Start rnove ahead by one character. word. line. and pangnph respectively move bac kwards by one chancter. word. line. and parapiph rnow the tex, cursor ,fier the last charactcr (End) and bçforc the firsr (Homs): * scroll the view up and down by one page and rnove the tert cursor up to the top line of the visible page togçles an extend mode. For example, when the extend mode is Ani selecred, text will be selected baçed upon the next text cursor movernents. Choosing stops the extend mode. Strategy 2: Scanning Text Keys This method is similar to usinç a standard keyboard. Le.. selecting movement keys to move the cursor over the text. Keys are drfined within the on-screen keyboard to move the text cursor in blocks (word. paragaph. home. end. page up and page down). Each key automatically repeats until a switch is activated. This gives the impression that the cursor is scaming the text. move the cursor ahead by character, word. line. and paragraph a move the cursor backwards by character. word. line. and paragraph a move the text cursor alter the last character (End) and befbre the fint (Hotne): scroll the vieu up and down by one page and rnove the insertion point up to the top line of the visible page toggles an rxtend mode. For example. when the ertend mode is first selected. text will be selectcd based upon the nrxt movernent. Choosing stops the extend mode. Fint choose the key that wil1 rnove the text cursor closest to the target location without overshooting the target. The character, word, line and paragraph movement keys are repeated at a rate equal to the scan rate. Activating the select or cancel switch stops the cursor and retums scanning to the keyboard. When scanning across the text, pay attention to the scanning text cursor and stop it when the cursor is at the target location or when the next block move will overshoot the target. In the latter case, you will then choose another movement key that will move the cursor closest to the target location without overshooting the target. Strategy 3: Sequential Scanning Text Keys The on-screen keyboard contains keys that are similar to standard keys that move the cursor over the text. Keys are defined within the on-screen keyboard to move the insertion point in blocks (word, paragraph. home, end, page up and page down). However, this method extends the notion of scanning to the text area. Each key automatically repeats until the select switch is activated, then the text cursor continues moving according to the next smaller block movement without having to explicitly select another key. This gives the impression that the cursor is scanning the text in a block pattern. For example, the paragraph key Stans the cursor scanoing by paragraphs, then by lines, words, and characters. To allow quick correction, it is assumed that if you make a mistake, it is by overshooting the target by only a block. Once you have moved backwards by the correct block, you then start scanning fonvard by the next smaller block. \i K B 2 El Start move the text cursor ahead by characters; words & characters; lines, words & characters; and paragraphs, lines, words & characters respectively When moving down by lines, the cursor is always positioned at the beginning of the line. Thus, any wordkharacter in that line cm then be chosen through fonvard scanning. When moving by words, the cursor is always positioned at the first character of the word. * *$ *-..--- *.'3 move the text cursor: - backwards by chancters; - backwards by words & fonvard by chanctee: - backwards by lines. & forward by words and characters: - and backwards by paragraphs. & fonvard by Iines. words and characters respectively When moving up by lines. the cursor is always positioned at the beginning of the line. This rnsures that any wordkharacter in that line can then be chosen through fonvard scanning. When moving by words. the cursor is always positioned ai the tint character of the word. '' rnove the text cursor afier the las, character (End) and befbre the first (Home): 2 scroll the vieiv up and down by one page and move the trrt cursor up to the top -line of the visible page toçglcr an cxtend mode. For example, when the extend mode is fint nelrctcd. text a41 be selected based upon the next text cursor rnovernentç. Choosing a stops the rxtend mode. First choose a tea cursor movement key to begin with. select the key that will move the cursor closest to the target location without overshooting the target. For examplr. if the target is in the nrxt paragaph or beyond. choose the fonvard paragraph key. The character. word. line and paragraph movement keys are repeated at a rate equal to the scan rate. Whçn scanning across the text. pay attention to the scanning text cursor and activate the select switch when the next block move will overshoot the target. Activating the select switch stops the current repeating block movrment and begins the next smaller repeating block movement. The text cursor pauses at the first character of the smaller block giving you a chance to select it without advancing the cunor. Continue until the cursor is repeating at the character level and activate the select switch when the target is reached. Scanning then retums to the keyboard. If the cursor reaches the target before scanning characters (e-g.,when the target is the first character in a paragraph, line or word). activate the cancel switch to stop the cursor and retums scaming to the keyboard. Altemately, repeatedly activate the select key to step through the levels without advancing. Strategy 4: Text Scanning The on-screen keyboard contains keys that are similar to standard keys that move the text cunor over the text. Keys are defined within the on-screen keyboard to move the insertion point in blocks (word. paragaph. home. end. page up and page down). However, this method extends the notion of scanning to the text area. When a text cursor movrment key is chosen. blocks of text (e-g., lines ) are highlighted or scamed starting from the current cursor location. This is similar to highlighting rows in the on-screen keyboard. Scaming continues until the select switch is activated at which point the next smallrr block is highlighted (e.g..words) without having to explicitly select another ksy. Scanning continues uniil the select switch is activated again. This continues unril the target location is reached. This gives the impression that the cursor is scanning the text in blocks. To allow quick correction, it is assumed that if you make a mistake, it is by overshooting the target by only a block. Once you have moved backwards by the correct block. you then stan scanning fonvard by the next smaller block. k K $ 2 Start a . .. highlight and scan the text: - fonvard by characters; - forward by words & characters: - forward by hies, words & characten; and - fonvard by paragaphs, lines, words & characters respectively When switching from scanning lines to words, scaming begins with the first word. * *$ *---- *;JF- highlightandscanthetext: - backwards by c haracters: - backwards by words & fonvard by charactrrs; - backwards by lines. & fonvard by words and characten; - and backwards by paragraphs, & fonvard by lines. words and charactrn respectively When switching from scanning lines to words. scanning begins with the first word in the line. Thus. any wordkharacter in that line can then be chosen through fonvard scanning. ' ,ove the text cursor ,fier the last character (End) and before the first (Horne): scroll the view up and down by one page and move the trat cursor up to the top linr of the visible page toggles an ertend mode. For example. when the ertend mode is first selected. tcxt will be selected based upon the next rnovements. Choosing stops the extend mode. First choose a trxt cursor movement key to begin with. select the paragraph key if the target is btyond the curent paragraph: othenvise, the line key if the target is beyond the curent linr: or othenvise. the word key if the target is beyond the current word. The character. word. linr and paragaph movemrnt keys are repeatrd at a rate rqual to the scan rate. When scamins across the text. pay attention to the target and activatr the select switch when the target is highlighted. The text cursor pauses at the first smaller block giving you a chance to select it. Continue activating the select switch whenever the target is contained in the highlighted block until the desired target character is highlighted. After you select the target with the select switch. scanning retums to the keyboard. If the cursor reaches the target before scaming characters (eg. when the target is the first character in a paragraph, line or word). activate the cancel switch to stop the cursor and retums scaming to the keyboard. Altemately, repeatedly activate the select key to step through the levels without advancing. Subject Reports What was the easiest part of performing the tasks? What was the hardest pan of performing the tas ks'? What specific likes and dislikes do you have of the sca~ingmethod that you used? What strategirs did you use to move the cursor in the following situations? target was horizontally ciose target was vrnically close target was horizontally distant target was verticaliy distant target was near end of a "word" target \vas missed If you felt any frustration in performing the tasks. please describe the reasons for your frustration. Please describe your degree of control in moving the cursor. Appendix E Condensed Data: Evaluation 1 Table E-1: Average total number of WiViK keys selectea (5 subjects x 2 sessions) to complete each task Strategy 1 Strategy 2 3Strategy 3 Strategy 4 SessGr 1 2 1 2 1 2 1 2 1 13.6 13.5 6.1 6.3 5.0 4.7 4.4 4.2 2 18.5 19.1 8.3 8.2 4.8 4.1 4.7 4.1 3 11.3 10.4 6.1 6.0 4.4 4.1 4.4 4.7 4 16.1 19.8 9.4 9.6 4.9 5.2 4.1 4.3 5 11.5 1 1.5 5.6 5.3 4.4 4.6 4.5 4.5 6 14.5 13.8 8.4 8.1 4.2 4.2 4.8 4.6 7 20.2 20.2 10.3 10.0 4.9 5.1 4.7 4.1 8 12.0 11.3 6.0 6.2 4.6 4.5 4.5 4.4 9 19.8 20.9 9.3 8.8 4.5 4.5 4.5 4.0 10 15.8 15.2 8.2 8.7 4.7 5.1 4.2 4.1 11 18.5 17.5 8.3 7.7 6.0 5.6 5.7 4.2 12 13.7 15.3 8.2 8.1 6.2 5.1 4.5 4.2 13 23.2 22.2 9.4 8 -7 4.7 4.7 4.3 4.4 14 18.0 17.4 10.5 9.4 4.8 4.8 4.0 4.1 15 15.2 13.6 7.6 7.6 4.4 4.5 4.4 4.3 16 9.4 8.5 5.1 5.2 4.8 4.8 4.8 4.3 17 16.7 17.6 9.4 9.0 5.8 5.7 4.6 4.6 18 16.1 16.0 9.7 9.2 5.0 5.4 4.7 4.3 19 17.0 16.8 7.5 6.9 4.7 4.9 5.1 4.2 20 10.9 11.1 6.9 6.6 4.6 4.8 4.4 4.4 21 17.9 17.1 7.8 7.5 4.6 4.4 4.2 4.1 22 21 -7 20.4 8.4 8.6 5.0 5.1 4.4 4.2 23 16.5 17.4 8.6 8.7 5.3 6.0 4.6 4.4 24 20.2 18.6 7.8 7.7 5.1 5.6 4.2 4.2 25 17.2 17.5 8.4 8.3 5.0 4.6 4.4 4.5 . 1 Avg . 16.2 1 16.1 8.1 7.9 4.9 4.9 4.5 4.3 Avg. 16.2 8.0 4.9 4.4 & Table E-2: Average total WiViK key selections (5 subjects x 2 sessions) per beginning point and the end point Strategy 1 Strategy 2 3Strategy 3 Strategy 4 Pos'n 1 2 1 2 1 2 1 2 1 10.3 1.4 3.1 1.1 1.5 1.8 1.6 1.1 2 7.0 9.9 2.7 3.6 1 -2 1.3 1.1 1.2 3 1.2 7.7 1 .O 3.1 1.2 1.1 1.2 1.4 4 8.1 7.9 3.5 4.0 1.8 1.3 1.3 1 .O 5 1.4 8.2 1.1 2.4 1.2 1.4 1.3 1.3 6 4.6 8.2 2.0 4.4 1.2 1.1 1.3 1.4 7 10.9 7.8 4.3 4.1 1.7 1.4 1 -2 1.3 8 7.2 2.5 3.1 1.O 1 .O 1.6 1.3 1.6 9 9.1 9.8 3.9 3.4 1.2 1.4 1.2 1.1 10 7.9 5.6 3.2 3.2 1.4 2.1 1.4 1.2 11 9.2 6.9 2.4 3.6 1.6 2.3 1.7 1.3 P 12 8.3 4.3 3.3 2.9 2.0 1.7 1.2 1.2 13 12.0 8.7 4.0 3.0 1.5 1.3 1.3 1.2 14 9.5 6.9 4.1 3.9 1.4 1.5 1.3 1.O 15 4.4 8.4 2.2 3.5 1.2 1.3 1.3 1.2 I 16 4.9 2.0 2.2 1.O 1.5 1 -4 1.4 1.3 17 6.5 9.0 3.4 3.9 1.9 1.9 1.8 1.4 18 8.0 6.8 4.1 3.6 1.8 1.5 1.4 1.3 19 7.5 7.4 2.5 2.8 1.3 1.5 1.3 1.2 20 4.8 4.2 2.1 2.7 1.2 1.5 1.3 1.3 21 8.0 8.6 2.1 3.6 1.1 1.4 1.2 1.2 22 7.5 11.9 2.5 3.9 1.6 1.5 1.4 1.2 23 7.8 7.5 3.3 3.4 2.0 1.7 1.5 1.4 24 9.1 9.2 2.1 3.8 1.4 2.0 1.7 1.1 25 5.0 10.5 3.0 3.4 1.4 1.4 1.4 1.2 1 I Avg . 7.2 7.2 2.8 3.1 1.4 1.5 1.3 1.2 Table E-3: Average number of select switch activations (5 subjects x 2 sessions) to complete each task Strategy 1 Strategy 2 3Strategy 3 Strategy 4 SessGr 1 2 1 2 1 2 1 2 1 28.0 27.7 16.5 17.1 16.2 16.0 15.4 14.4 2 38.7 39.1 23.2 23.1 17.5 16.5 18.0 16.2 3 23.1 21.1 16.6 16.0 15.7 13.9 16.9 16.9 4 33 -4 41 -1 26.2 27.0 16.7 18.4 15.5 15.9 5 24.1 23.8 14.9 14.0 14.4 14.6 15.7 15.5 6 31.1 30.0 23.5 22.4 16.0 14.8 18.3 17.6 7 42.5 42.9 29.0 28.6 17.3 18.1 18.1 16.1 ----8 24.5 23.6 16.2 16.7 ----15.1 15.0 14.6 14.8 9 41.1 44.2 26.4 18.1 17.1 17.6 16.0 10 31.8 30.9 23.1 23.8 15.2 16.6 14.6 14.6 11 38.8 35.8 23.6 20.9 18.6 17.0 19.5 15.8 1 12 28.4 31 -5 22.7 22.6 19.5 17.2 15.9 15.0 13 47.2 45.1 26.5 24.6 17.3 18.3 16.1 16.6 14 36.9 36.1 29.7 26.3 18.4 18.3 15.7 16.6 15 31 -6 28.6 21.4 21.1 15.5 15.2 16.1 15.4 16 20.3 18.1 13.6 13.5 16.0 15.0 16.3 14.4 17 34.4 36.0 26.6 25.7 19.3 18.2 16.8 16.9 18 34.8 34.1 26.9 25.9 17.7 18.3 17.7 16.2 19 34.7 34.0 20.6 18.7 15.3 17.0 17.0 14.9 20 22.2 22.8 18.8 17.6 16.1 17.3 16.8 16.5 21 37.9 35.4 21.3 20.6 15.8 15.5 15.9 15.2 22 44.9 42.0 23.4 23.5 15.5 16.9 15.8 15.8 23 33.6 36.3 23.1 23.6 16.9 17.8 17.1 15.8 24 40.9 38.9 21 -5 21 -9 15.9 17.3 14.1 14.3 25 36.6 35.7 23.6 22.8 18.1 17.5 17.5 17.3 l Avg. 33.7 33.4 22.4 21.7 16.7 16.7 16.5 15.8 206 Table E-4: Arctangent of average proportion of cancel switch activations trial (5 subjects x 2 sessions) to complete each task with respect to total number of switch activations per trial 1 1 Strategy 1 1 Strategy 2 / 3Strategy 3 1 Strategy 4 SessGr 1 2 1 2 1 2 1 2 1 0.02 0.01 0.02 0.01 0.08 0.05 0.07 0.06 2 0.04 0.02 0.01 0.02 0.05 0.02 0.05 0.01 3 0.02 0.00 0.01 0.01 0.06 0.05 0.02 0.05 4 0.03 0.03 0.01 0.03 0.07 0.04 0.01 0.03 5 0.04 0.02 0.01 0.01 0.06 0.08 0.04 0.04 6 0.03 0.03 0.02 0.03 0.04 0.05 0.03 0.02 7 0.03 0.02 0.03 0.03 0.04 0.07 0.03 0.01 8 0.01 0.02 0.01 0.02 0.06 0.06 0.06 0.05 9 0.01 0.02 0.02 0.03 0.05 0.04 0.03 0.01 10 0.00 0.01 0.01 0.01 0.04 0.05 0.02 0.02 11 0.04 0.02 0.05 0.03 0.1 1 0.1 O 0.1 O 0.02 12 0.03 0.03 0.03 0.03 0.1 1 0.08 0.02 0.01 13 0.02 0.02 0.02 0.03 0.05 0.03 0.02 0.03 14 0.03 0.03 0.01 0.00 0.04 0.03 0.01 0.01 15 0.04 0.02 0.02 0.02 0.05 0.04 0.02 0.02 16 0.05 0.04 0.02 0.01 0.08 0.1 O 0.06 0.05 17 0.03 0.01 0.04 0.04 0.09 0.1 1 0.03 0.05 18 0.06 0.04 0.01 0.03 0.05 0.08 0.05 0.02 19 0.02 0.01 0.03 0.02 0.08 0.03 0.04 0.01 20 0.02 0.02 0.02 0.02 0.07 0.05 0.01 0.03 21 0.03 0.01 0.01 0.03 0.05 0.05 0.01 0.01 22 0.03 0.02 0.03 0.02 0.09 0.08 0.03 0.02 23 0.02 0.03 0.03 0.02 0.1 O 0.1 1 0.04 0.03 24 0.01 0.02 0.00 0.02 0.08 0.08 0.03 0.03 25 0.02 0.02 0.01 0.01 0.05 0.04 0.02 0.02 L Avg. 1 0.03 0.02 0.02 0.02 0.07 0.06 0.03 0.03 Table E-5: Average Total Tme (5 subjects x 2 sessions) to complete each of the 25 tasks 1 1 Strategy 1 1 Çtrategy 2 1 3Strategy 3 1 Stategy 4 ------24 74.0 1 67.9 54.5 54.4 57.0 60.5 59.2 57.4 25 69.6 67.8 56.0 51.8 51.9 50.3 58.2 54.3 Avg . 71 .f 67.0 55.5 53.4 54.6 52.2 61.5 56.2 Appendix F Statistical Analyses: Evaluation 1 Dependent: Total WiViK Keys Used ANOVA Source DF Type I SS Mean Square F Value Pr> F Scan Strategy 3 44235.6 1478 -5 568.2 0.0001 Session Group 1 0.9 0.9 0.4 0.5499 Trial Pattern 24 275.9 11.5 4.4 0.0001 Student-Newman-Keuls Test (Means with the same letter are not significantly different) SNK Grouping Mean N Scan Strategy Alpha= 0.05 df= 17 1 MSE= 2.672331 Number of Means 2 3 4 Critical Range 0.6453689 0.7730 125 0.5482555 SNK Grouping Mean N Session Group A 8.5 100 1 A 8.3 100 2 Alpha= 0.05 df- 17 1 MSE= 2.672334 NumberofMeans 2 Critical Range 0.4563447 Dependent: Total WiViK Keys to Set Insertion Point Source DF Type I SS Mean Square F Value Pr>F Scan Strategy 3 2307.9 769.3 445.3 0.0001 Beg/End Position 1 0.7 0.7 0.4 . 0.5158 Trial Pattern 24 144.1 6.0 3.5 0.0001 Student-Ne wman-Keuls Test (Means with the same lrtter are not significantly different) SNK Grouping Mean N Scan Strategy A 7.20 100 1 B 2.98 1O0 2 C 1-46 1O0 3 C 1.21 100 4 Alpha= 0.05 df= 370 MSE= 1.72749 1 Number of Means 2 3 4 Cri t ical Range 0.3655056 0.4371 0.479704 1 SNK Grouping Mean N Session Group A 3.24 200 1 A 3.19 200 2 Alpha= 0.05 de370 PUISE= 1.72749 1 Number of Means 2 Critical Range 0.25845 1 5 SNK Grouping Mean N Position A 3.26 200 1 A 3.17 200 2 Alpha= 0.05 df- 4 MSE= 34.5 Number of Means 2 Critical Range 0.25845 15 Dependent: Select Switch Activations ANOVA Source DF Type l SS Mean Square F Value Pr, F Scan Strategy 3 9743.6 3247.9 302.4 0.0001 Session Group 1 8.4 8.4 0.8 0.3784 Trial Pattern 24 1766.7 73.6 6.9 0.0001 Student-Newman-Keuls Test (Means with the sarnr letter are not significantly different) SNK Grouping Mean N Scan Strategy A 33.53 50 1 Alpha= 0.05 df= 17 1 MSE= 10.74003 Number of Means 2 3 4 Critical Range 1 -2937951 1 -5496869 1.7005295 SNK Grouping Mean N Session Group A 22.3 1 O0 1 A 21.9 1 O0 2 - -- -- pp Alpha= 0.05 df= 168 MSE= 10.9074 1 Number of Means 2 Critical Range 0.9220699 Dependent: Cancel Switch Oh Usage (ArcTangent Transformed) ANOVA Scan Strategy 3 0.057 0.01 9 85.78 0.0001 Session Group 1 0.001 0.001 5.1 3 0.0248 1 Trial Pattern ( 24 1 0.019 1 0.001 1 3.62 1 0.0001 1 Student-Newrnan-Keuls Test (Means with the same lrtter are not significantly different) SNK Grouping Mean N Scan Strategy A 0.063 50 3 B 0.033 50 4 C B 0.025 50 1 C 0.020 50 2 Alpha= 0.05 de171 .ME= 0.0002 19 Number of Means 2 3 4 Critical Range 0.005 848 0.0070046 0.0076864 SNK Grouping Mean N Session Group A 0.037 1O0 1 B 0.032 1O0 2 Number of Means Z Critical Range 0.004 1352 Dependent: Total Time ANOVA Source DF Type I SS Mean Square F Value PrwF Scan Strategy 3 7692.1 2564.0 81.6 0.0001 Session Group 1 601 -1 601.1 19.1 0.0001 Trial Pattern 24 16225.8 676.1 21.5 0.000 1 1 Scan ' Session 1 3 1 84.6 1 28.2 1 0.9 1 0.4446 1 Student-Newman- Keuls Test (Means with the same letter are not sipificantly different) SNK Grouping Mean N Scan Strategy A 69.1 50 1 B 58.8 50 4 C 54.4 50 2 Alpha= 0.05 de17 1 MSE= 3 1-421 15 Number of Means 2 3 4 Ct-Îtical Range 2.2 129608 2.6506488 2.908656 1 SNK Grouping Mean N Session Group A 60.7 1O0 1 B 57.2 1O0 2 Alpha= 0.05 df= 1 7 1 MSE= 3 1-421 15 Number of Means 2 Cntical Range 1.5647996 Dependent: Count of Overshooting Target ANOVA Source DF Type l SS Mean Square F Value Pr > F Scan Strategy 3,4 1 1922 1 922 55.7 0.001 7 Session Group 1 98 98 2.8 O. 1672 BegIEnd Position 1 450 450 13.0 0.0225 Student-Newman-Keuls Test (Mrans with the same Istter are not sigificantly different) 1 SNK Grouping ( Mean 1 N 1 scanstrategy 1 Alpha= 0.05 df= 1 MSE= 34.5 Number of Means 2 Critical Range 1 1.53 1492 SNK Grouping Mean N Session Group A 49.5 4 1 Alpha= 0.05 de4 MSE= 34.5 Nurnber of Means 2 Critical Range 11.531492 SNK Grouping Mean N Position A 53.5 4 1 8 38.5 4 2 Alpha= 0.05 df= 4 MSE= 34.5 Nurnber of Means 2 Critical Range 1 1.53 1492 Dependent: Count of Undershooting Target ANOVA Source DF Type f SS Mean Square F Value Pr>F Scan Strategy 3,4 1 180.5 180.5 2.7 0.1767 Session Group 1 112.5 11 2.5 1.7 0.2655 Beg/End Position 1 72.0 72.0 1.1 0.3593 L Student-Newman-Keuk Test (Means with the same lrtter are not significantly different) SNK Grouping Mean N Scan Strategy A 20.75 4 3 A 1 1 -25 4 4 Alpha= 0.05 df= 4 MSE= 67.15 Number of Means -3 Critical Range 16.09986 SNK Grouping Mean N Session Group A 19.75 4 1 Alpha= 0.05 df= 4 MSE= 67.25 Number of Means 2 Critical Range 16.09986 SNK Grouping Mean N Position A 19 4 2 A 13 4 1 L Alpha= 0.05 df= 4 MSE= 67.25 Number of Means 2 Cntical Range 16.09986 Table F- 1 :Predicted vs. actual total selected keys ( Strategy 1 1 Strategy 2 ] Strategy 3 1 Pred, Actual Diff. Pred. Actuai Diff. Pred. Actual Diff. Pred. ActuaI Diff. 1 13.0 13.6 0.6 6.0 6.2 0.2 4.0 4.8 0.8 4.0 4.3 0.3 2 19.0 18.8 -0.2 9.0 8.3 -0.8 4.0 4.5 0.5 4.0 4.4 0.4 ------.- . - -- - 3 10.0 10.9 0.9 6.0 6.1 0.0 4.0 4.3 0.3 4.0 4.6 0.6 4 25.0 18.0 -7.1 9.0 9.5 0.5 4.0 5.1 1.1 4.0 4.2 0.2 5 10.0 11.5 1.5 5.0 5.5 0.5 4.0 4.5 0.5 4.0 4.5 0.5 6 22.0 14.2 -7.9 9.0 8.3 -0.8 4.0 4.2 0.2 4.0 4.7 0.7 7 27.0 20.2 -6.8 10.0 10.2 0.2 4.0 5.0 1.O 4.0 4.4 0.4 8 12.0 11.7 -0.4 6.0 6.1 0.1 4.0 4.6 0.6 4.0 4.5 0.5 9 22.0 20.4 -1.7 9.0 9.1 0.1 4.0 4.5 0.5 4.0 4.3 0-3 10 15.0 15.5 0.5 8.0 8.5 0.4 4.0 4.9 0.9 4.0 4.2 0.2 11 21 .O 18.0 -3.0 8.0 8.0 0.0 4.0 5.8 1.8 4.0 5.0 1-0 12 26.0 14.5 -11.5 9.0 8.2 -0.9 4.0 5.7 1.7 4.0 4.4 0.4 13 21.0 22.7 1.7 8.0 9.1 1.1 4.0 4.7 0.7 4.0 4.4 0.4 14 23.0 17.7 -5.3 9.0 10.0 0.9 4.0 4.8 0.8 4.0 4.1 0.0 15 15.0 14.4 -0.6 8.0 7.6 -0.4 4.0 4.5 OS 4.0 4.4 0.4 16 11.0 9.0 -2.1 6.0 5.2 -0.9 4.0 4.8 0.8 4.0 4.6 0.6 17 34.0 17.2 -16.9 9.0 9.2 0.2 4.0 5.8 1.8 4.0 4.6 0.6 18 23.0 16.1 -7.0 10.0 9.5 -0.6 4.0 5.2 1.2 4.0 4.5 0.5 19 16.0 16.9 0.9 6.0 7.2 1.2 4.0 4.8 0.8 4.0 4.7 0.7 20 11.0 11.0 0.0 7.0 6.8 -0.3 4.0 4.7 0.7 4.0 4.4 0.4 21 20.0 17.5 -2.5 7.0 7.7 0.7 4.0 4.5 0.5 4.0 4.2 0.2 22 25.0 21.1 -4.0 8.0 8.5 0.5 4.0 5.1 1.1 4.0 4.3 0.3 23 28.0 17.0 -11.1 7.0 8.7 1.7 4.0 5.7 1.7 4.0 4.5 0.5 24 25.0 19.4 -5.6 8.0 7.8 -0.3 4.0 5.4 1.4 4.0 4.2 0.2 25 17.0 17.4 0.4 10.0 8.4 -1.7 4.0 4.8 0.8 4.0 4.5 0.5 Avg. 19.6 16.2 -3.5 7.9 8.0 0.1 4.0 4.9 0.9 4.0 4.4 0.4 f-stat. -3.6 0.5 9.7 10.3 Table F-2: Predticted vs. actual total select switch activations Pred. Actual Diff. Pred. Actual Diff. Pred. Actual Diff. Pred. Actual Diff. 1 26.0 27.9 1.9 16.0 16.8 0.8 15.0 16.1 1.1 15.0 14.9 -0.1 2 38.0 38.9 0.9 25.0 23.2 -1.9 16.0 17.0 1.0 16.0 17.1 1.1 3 20.0 22.1 2.1 16.0 16.3 0.3 16.0 14.8 -1.2 16.0 16.9 0.9 4 50.0 37.3 -12.8 25.0 26.6 1.6 16.0 17.6 1.6 16.0 15.7 -0.3 5 20.0 24.0 4.0 13.0 14.5 1.5 15.0 14.5 -0.5 15.0 15.6 0.6 6 44.0 30.6 -13.5 25.0 23.0 -2.1 16.0 15.4 -0.6 16.0 18.0 2.0 7 54.0 42.7 -11.3 28.0 28.8 0.8 16.0 17.7 1.7 16.0 17.1 1.1 8 24.0 24.1 0.1 16.0 16.5 0.4 15.0 15.1 0.1 15.0 14.7 -0.3 9 44.0 42.7 -1.4 25.0 25.9 0.9 16.0 17.6 1.6 16.0 16.8 0.8 10 30.0 31.4 1.4 22.0 23.5 1.5 14.0 15.9 1.9 14.0 14.6 0.6 11 42.0 37.3 -4.7 22.0 22.3 0.3 16.0 17.8 1.8 16.0 17.7 1.7 12 52.0 30.0 -=.1 25.0 22.7 -2.4 15.0 18.4 3.4 15.0 15.5 0.4 13 42.0 46.2 4.2 22.0 25.6 3.6 16.0 17.8 1.8 16.0 16.4 0.4 14 46.0 36.5 -9.5 25.0 28.0 3.0 16.0 18.4 2.4 16.0 16.2 0.1 15 30.0 30.1 0.1 22.0 21.3 -0.8 15.0 15.4 0.4 15.0 15.8 0.8 16 22.0 19.2 -2.8 16.0 13.6 -2.5 16.0 15.5 -0.5 16.0 15.4 -0.7 17 68.0 35.2 -32.8 25.0 26.2 1.2 16.0 18.8 2.8 16.0 16.9 0.9 18 46.0 34.5 -11.6 28.0 26.4 -1.6 16.0 18.0 2.0 16.0 17.0 0.9 19 32.0 34.4 2.4 16.0 19.7 3.7 15.0 16.2 1.2 15.0 16.0 0.9 20 22.0 22.5 0.5 19.0 18.2 -0.8 16.0 16.7 0.7 16.0 16.7 0.6 21 40.0 36.7 -3.4 19.0 21.0 2.0 15.0 15.7 0.7 15.0 15.6 0.6 22 50.0 43.5 -6.6 22.0 23.5 1.5 15.0 16.2 1.2 15.0 15.8 0.8 23 56.0 35.0 -21.1 19.0 23.4 4.4 15.0 17.4 2.4 15.0 16.5 1.5 24 50.0 39.9 -10.1 22.0 21.7 -0.3 14.0 16.6 2.6 14.0 14.2 0.2 25 34.0 36.2 2.2 28.0 23.2 -4.8 16.0 17.8 1.8 16.0 17.4 1.4 Avg. 39.3 33.5 -5.8 21.6 22.0 0.4 15.5 16.7 1.2 15.5 16.2 0.7 1-stat. -3.1 0.9 5.4 5.4 Table F-3: Predicted vs. actual total times Strategy 1 Strategy 2 Strategy 3 Strategy 4 Pred. Actual Diff. Pred. Actual Diff. Pred. Actual Diff. Pred. Actual Diff. 1 49.0 49.7 0.7 39.6 40.3 0.7 47.5 49.6 2.1 49.5 54.3 4.8 2 83.7 83.2 -0.5 61.9 58.6 -3.2 48.5 55.1 6.6 49.5 61.1 11.6 3 44.6 41.9 -2.6 38.6 38.2 4.4 42.1 44.0 1.9 44.1 53.7 9.7 4 91.1 78.4 -12.6 65.3 63.8 -1.5 51.5 56.9 5.4 53.0 58.4 5.4 5 43.6 41.5 -2.0 33.2 35.3 2.2 41.1 42.3 1.2 43.1 50.1 7.0 6 99.5 70.1 -29.4 64.8 57.6 -7.2 42.1 45.2 3.1 43.6 60.7 17.1 7 118.3 93.3 -25.0 71.8 72.4 0.6 50.5 59.8 9.3 52.0 63.5 11.5 8 48.5 50.9 2.4 38.1 37.8 -0.4 48.0 47.5 -0.5 49.5 57.7 8.2 9 85.6 81.1 -4.6 60.4 63.6 3.3 54.0 63.1 9.1 54.9 65.9 11.0 10 55.9 55.5 -0.4 45.0 48.0 3.0 44.1 47.4 3.4 47.5 51.5 4.0 11 82.7 81.6 -1.1 56.4 59.4 2.9 54.0 54.0 0.0 55.4 68.5 13.1 12 102.0 66.7 -35.3 65.3 56.2 -9.1 50.0 58.1 8.1 51.5 56.4 4.9 13 78.2 88.2 9.9 55.4 66.6 11.1 55.4 62.4 6.9 57.4 65.9 8.5 14 89.1 72.7 -16.4 62.9 65.8 3.0 50.0 58.4 8.4 51.5 58.2 6.7 15 61.9 63.2 1.3 49.5 49.8 0.3 43.6 46.8 3.3 44.1 52.8 8.8 16 54.9 51.9 -3.0 41.6 38.6 -2.9 44.6 45.5 0.9 46.5 52.2 5.7 17 116.8 74.0 -42.8 72.8 65.3 -7.4 62.4 66.3 3.9 63.9 71.4 7.5 18 92.6 80.9 -11.7 67.3 64.2 -3.1 58.4 66.0 7.6 58.9 68.7 9.8 19 65.3 69.4 4.1 42.1 48.1 6.0 47.0 51.7 4.7 48.0 58.8 10.8 20 47.0 50.5 3.5 43.6 42.2 -1.4 37.6 42.7 5.1 38.6 46.5 7.9 21 89.1 79.1 -t0.0 53.0 54.2 1.2 44.1 46.6 2.6 45.0 52.4 7.3 22 93.1 85.3 -7.8 59.4 60.6 1.2 55.9 59.9 4.0 57.4 66.3 8.8 23 118.3 78.5 -39.8 60.9 65.6 4.7 49.0 56.0 7.0 50.0 61.1 11.2 24 87.6 70.9 -16.7 57.4 54.4 -3.0 51.5 58.8 7.3 53.0 58.3 5.3 25 67.8 68.7 0.9 61.4 53.9 -7.5 43.6 51 .l 7.6 44.6 56.2 11.7 Av~. 78.6 69.1 -9.6 54.7 54.4 -0.3 48.6 53.4 4.8 50.1 58.8 8.7 T-stat. -3.3 -0.3 8.1 14.2 Appendix G Predicted Times With Keyboard Rearrangement ------Strategy 1 Strategy 2 Strategy 3 Strategy 4 Orig New Diff. Orig New Diff. Orig New Diff. Orig New Diff. 1 45.0 42-6 2.5 39.6 31.2 8.4 47.5 37.6 9.9 49.5 39.6 9.9 2 73.3 62.4 10.9 53.0 44.6 8.4 48.5 37.6 10.9 49.5 38.6 10.9 3 35.6 26.7 8.9 38.6 29.7 8.9 42.1 31.2 10.9 44.1 33.2 10.9 4 66.8 64.4 2.5 61.9 54.9 6.9 51.5 40.6 10.9 53.0 42.1 10.9 5 36.1 39.6 -3.5 33.2 26.2 6.9 41.1 31.2 9.9 43.1 33.2 9.9 - .. - - - - - 6 58.9 57.4 1.5 45.0 38.6 6.4 42.1 31.2 10.9 43.6 32.7 10.9 7 74.7 74.3 0.5 60.4 54.0 6.4 50.5 39.6 10.9 52.0 41.1 10.9 8 44.6 37.6 6.9 38.1 31.7 6.4 48.0 38.1 9.9 49.5 39.6 9.9 9 56.9 63.4 -6.4 57.4 50.5 6.9 54.0 43.1 10.9 54.9 44.1 10.9 10 50.5 53.5 -3.0 45.0 43.1 2.0 44.1 35.1 8.9 47.5 38.6 8.9 11 69.3 59.9 9.4 45.0 38.6 6.4 54.0 43.1 10.9 55.4 44.6 10.9 12 57.4 52.0 5.4 51.5 44.6 6.9 50.0 40.1 9.9 51.5 41.6 9.9 13 70.3 73.8 -3.5 55.4 51.0 4.5 55.4 44.6 10.9 57.4 46.5 10.9 14 69.8 57.9 11.9 58.9 53.5 5.4 50.0 39.1 10.9 51.5 40.6 10.9 15 51.0 40.1 10.9 45.5 37.1 8.4 43.6 33.7 9.9 44.1 34.2 9.9 16 42.1 28.2 13.9 32.7 23.8 8.9 44.6 33.7 10.9 46.5 35.6 10.9 17 60.4 50.0 10.4 52.0 42.1 9.9 62.4 51.5 10.9 63.9 53.0 10.9 18 68.3 67.8 0.5 61.9 56.4 5.4 58.4 47.5 10.9 58.9 48.0 10.9 19 55.4 56.9 -1.5 42.1 38.1 4.0 47.0 37.1 9.9 48.0 38.1 9.9 20 46.5 36.6 9.9 34.2 26.7 7.4 37.6 26.7 10.9 38.6 27.7 10.9 21 66.8 55.9 10.9 47.0 40.6 6.4 44.1 34.2 9.9 45.0 35.1 9.9 22 75.7 73.3 2.5 59.4 54.0 5.4 55.9 46.0 9.9 57.4 47.5 9.9 23 60.4 51.0 9.4 51.0 41.6 9.4 49.0 39.1 9.9 50.0 40.1 9.9 24 66.8 62.4 4.5 46.5 41.1 5.4 51.5 43.6 7.9 53.0 45.0 7.9 25 58.9 56.4 2.5 47.0 42.1 5.0 43.6 32.7 10.9 44.6 33.7 10.9 Avg. 58.5 53.8 4.7 48.1 41.4 6.7 48.6 38.3 10.3 50.1 39.8 10.3 . Appendix H Subject Instructions: Evaluation 2 Overdrive Scanning Method 1 Two switches will be used to control the computer through a mcthod called "scanning." One switch (select) is used (clicked) to stop a moving highlight (scanning) when it reaches a desired target in an array of items. The other switch (overdrive) is used (held down) to advancr the highlight over the items at a faster rate. You will be presented with a horizontal array of 15 boxes. one of which will display a srnaller green box within it. and a single-key WiViK on-scrern keyboard as shown below: You will perfom four sets of trials, with each set including a practice. In borh practice and test trials. you will make 30 selections (selecting each box in the array twice). In the first set. you will only use the "select" switch. Trials begin with a dialog box displaying the message "Ready to begin trial ..." When you are ready. click the "select" switch once (with your dominant hand) to begin the trial. The dialog box will disappear and a highlight will begin moving lefi-ro-right across the 15 boxes displayed above. When the box containing the smaller green box is highlighted. click the "select" switch again to select it. Do your best to accurately select it. If you do not make any selrction. the trial will end automatically once the highlight moves nght of the last box. You carmot correct any missed selections. Imrnediately afirr a srlection (either correct or incorrect). the same dialog box as before is shown indicating the system is ready for you to begin the next trial. You may pause at this time. Repeat for al1 trials until a message indicatrs the trial set is over. In the second, third. and founh set of trials. you will use second switch (with the same hand). callsd the "overdrive" switch. While you hold down this switch. the highlight will advance across the array at a faster speed. When you release. the speed slows to the original rate. Threc different speeds will be tested. The specific order for using these different speeds is chosen through a random drawing at the beginning of the test. You will use the "overdrive" switch to move to the target location as quickly as you cm. You must. however, release this "overdrive" switch in time to accurately select the target with the "select" switch. Only use the "overdrive" when you feel confident that you can release it and select the target. Accurate selection is important. Overdrive Scanning Method 2 Two switches will be used to control the cornputer through a method called "scaming." One switch (select) is used (clicked) to stop a moving highlight (scanning) when it reaches a desired target in an array of items. The other switch (overdrive) is used (clicked) to toggle the speed of the moving highlight to a faster. You will be presentrd with a horizontal array of 15 boxes, one of which will display a smallrr green box within it. and a single-key WiViK on-screen keyboard as show below: You will perform four sets of trials. with each set including a practice. In both practice and test trials. you will makr 30 selections (selecting each box in the array twice). In the fini set. you will only use the "select" switch. Trials begin with a dialog box displaying the message "Ready to begin trial ..." When you are ready. click the "select" switch once (with your dominant hand) to begin the trial. The dialog box will disappear and a highlight will begin moving lefi-to-right across the 15 boxes displayed above. When the box containing the smaller green box is highlighted. click the "select" switch again to select it. Do your best to accurately select it. If you do not make any selection, the triai will end automatically once the highlight moves right of the last box. You cannot correct any missed selections. Immediately afier a selection (either correct or incorrect). the same diaiog box as before is shown indicating the system is ready for you to begin the next trial. You may pause at this time. Repeat for al1 trials until a message indicates the trial set is over. In the second. third. and fourth set of trials, you will use second switch (with the samr hand). called the "overdrive" switch which toggles the scan rate between slow and fast. When you click this switch. the highlight will advance across the array at a faster speed. When you click it again. the speed slows to the original rate. Thrre different speeds will be tested. The specific order for using these different speeds is chosen through a random drawing at the beginning of the test. You will use the "overdrive" switch to move to the target location as quickly as you cm. You must. howevrr. stop the "overdrive" in time to accurately select the target with the "select" switch. Only use the "overdrive" when you feel confident that you can start and stop it to select the target. Accurate selection is important. If you make a selection before toggling to the slower speed, you must toggle to the slower speed by clicking the "overdrive" switch before proceeding to the next trial. Appendix I Condensed Data: Evaluation 2 Overdrive Method 1 Average Times Table 1-1: Average times taken to select the target with Overdrive Method 1. Target Item Standard Scan Overdrive Scan Intewal Interval 0.66 0.33 1 0.22 0.1 1 Overdrive Method 2 Average Times Table 1-7: Average times taken to select the target with Overdrive Method 2. Target Item Standard Scan Overdrive Scan lntewal Interval 0.66 0.33 1 0-22 1 0.1 1 Appendix J Review of Design Guidelines for Alternative Access The Trace Research and Development Center has lead the field in developing guidelines for increasing the accessibility of computer systems (Vanderheiden, Lee, and Scadden. 1987; Vanderheiden. 1994). These guidelines focus on the design of both the standard hardware and of applications to be more accessible either immediately or through party alternate accrss solutions as described above. Thess guidelines provide genenc pidance in designing features ihat achieve achieving certain usability objectives for al1 areas of disability. Microsofi ( 1996) has rrcrntly published a set of guidelines for developers who design and producr computer software that accommodatrs users with disabilities. They discuss both accessibility features and detailed progamming techniques. Although the guidelines are too numerous to fully discuss. thrre are a few genrral concepts ponrayed that are relevant to the transparent input approach discussed here: Computer systems and applications should follow standard protocols interpreting keyboard and mouse input. This ensures that standard GIDE1 access systrms cm have complete transparent access. User operations should be simple. e-g..awkward keyboard mouse input. such as key-mouse combinations or multiple button clicks, should be minimized or eliminated. This reduces the complexity of input ro be generated by a GIDEI. AI1 actions should be achievable by keyboard actions alone, i.e., discrete selections rather than pointing device manipulations. This provides the option for an access system to perfom al1 operations via keystroke emulation. Applications should not fully take over the processor. This ensures that a software-only GIDEI can operate simultaneously as the application. Scanning on-screen keyboards, for example. require constant updating as they highlight items. Applications should use standard GUI objects and messages. This allows access system developers the possibility to directly engage these objects. Rather than move a cursor over top of the object or use keystroke equivalents, the access system could directly select it. An access system could also hide any pointing manipulations associated with these objects (e.g.. sequential actions) by interna11y sending a sequence of messages fol lowing a simple selection by the user. Keyboard navigation should follow a logical order. This allows the access system to also engage navigation logically and in a manner that can be pre-planned. This panicular design guideline can br exploited by a scanning system as suggested by my task transparency approach to systematically scan across objects. iMacDougal1 et al ( 1 9S8ab) also developed a set of accessibility design guideline. These differ from the above in that they relate specifically to the rnodel of alternative access that they descnbed. They addressed two audiences: guidelines for manufacturen of computer systems and guidelines for devrlopers of alternative access systems. The latter guidelines are relevant inasmuch as they reinforce the modularity of access systerns and access componrnts can be designed independent of keyboard and mouse input. These guidelines suggest that al1 access systems should contain or address al1 of the components of the model. New accsss componrnts can then be insrrted into the model or existing methods can be used in novel ways whilc maintaining the overall inte-gity of the model. Vanderheiden ( 1985) describes how a wide variety of selection-based access methods can be constructed and how performance might be measured, but offers no guidance to improve the usability of them nor how to best employ thern to perform specific tasks. Cress and Goltz ( 1989), also of the Trace Center, provide more usehl guidelines gathered fiom clinical and educational literature related to the cognitive factors affecting accessibility of computers and electronic devices. Although they do not directly target scaming methods, they express issues of relevance to such systems. With respect to inpdinterface controls and presentation format, these authors offer the following guidelines (Table J-1): INPUT/INTERFACE CONTROLS 1. Decrease visual and procedural cornplexity of control techniques. 2. Reduce number of differentchoices to perceive/select. 3. Minimize conceptual complexity of control techniques (e-g., memory). 4. Present choices in similar methods across different tasks. 5- Avoid switching contexts or operating modes without obvious clues. 6. Limit the possible number of results associated with a given action (such as pressing a particular switch. PRESENTATION FORMAT 1. Reduce visual and auditory complexity of the output display. 2. Minimize use of transitory signals. 3. Highlight important information on the display and group information in meaningful ways. 3. Provide direct task-related feedback to the user. 5. Limit the number of activities occurring simultaneously. 6. Match the means of concept representation to user skills Table J-1: Design guidelines for reducing cognitive demands to improve accessibility of cornputers and electronic devices (abbreviated from Cress and Goltz. 1989,p. 25-26): To the best knowledge of this author. there are no pubiished guidelines spscific to designing scanning access systems. Ovcr the course of the past 70 years. developers have brsn adding and deleting features drpcnding upon the reaction of users and following the lrad of other developers. As an expert in the field. this author offers the following mie-of-thumb guidelines chat are cornmon among scanning access systems: With an automatic or inverse scanning method, the scan interval should be constant and long enough such that the user can accurately respond wi th a switch activation (or release) (,Vanderheiden.1985). This interval must be adjustable to match the user abilities. The consistent interval provides a rhythm that allows users to prepare themselves to activate the switch. There should be an allowance for extra time following any selection to allow the user to recover and make a second selection if necessary, e.g.. to select the first item in a row after selecting the row. This interval must also be adjustable, although typically, this delay is equal to twice the scan rate (Shein et al. 1985). One developer uses a graduated delay (TetraScan') such that the scan rate gradually returns to the standard afier being delayed. 3. A separate delay time should be adjustable to indicate a selection afier a period of no switch activation with step. invene and directed scaming if no explicit switch is assigned for selection. 4. A sepante time should be adjustable to filter out any inadvertent switch activations. This is the time that the user must hold dom a switch to activate it. 5. A separate time should be adjustable to account for any switch bouncing afier a swi tch activation. This is the minimum time between successive switch activations. 6. Scanning should proceed le fi-to-righ t and top-to-bottom. This rnay be changed to nght-to-le fi for some cultures. 7. If the user misses selecting a taqet. the scaming should wraparound. sg. scans from the top afier scanning the bottom row. or scan from the left afier scanning the right-most column. 8. There should be a mechanism for the user to canceI or escape fiom scanning an unwanted situation (e.g..wrong row) and initiate sca~ingfrom the beginning. This may be accomplished with a separate switch. or by escaping afier a certain number of cycles of scanning at one level (e.g.. across a row), 9. Afier a selection. automatic and inverse scanning should start over at the highest levrl from a consistent starting point. An option should be available to allow the user to stop scanning at that point and not be distracted while concentrating on some othrr task. 10. The scanning indicator (highlight) should be highly visible so that the user can readily detemine which itsmigroup is being considered for selection. Typical indicaiors include: a light spot. a box border around the item/goup, and an invened background (e.g.. black on white keys or white on black keys.) 1 1. Feedback. visual adorauditory. should be provided to indicate when a selection has been made. 12. Auditory feedback indicating each scan interval should be optional. This feedback helps the user get into the 'rhythm' of scaming. ' Zygo Industries. Portland. OR 13. Items to be scanned should be mnged in meaningful groups so that they can be quickly located. and within groups they should be arranged by fiequency-of-use so that scanning time is rninimized. The overriding consideration is the cognitive abilities of the user and being able to locate items. eg.. an alphabetic arrangement of letters is easier to use by a new writer. 14. With automatic scanning. the user should be encounged to concentrate on the target item and activate the switch whenever it is highlighted, rather than track the scanning. This is repeated until the individual item is highlighted and selrcted. Appendix K Suggested Extensions to Other GUI Tasks Menus offer a direct way for users to select a comrnand without memonzing somc command keystrokes. For commands that are ussd frequently. it makes sense to include thèm in the on- screen keyboard whsre they can be directly selected. However. it is not practical to includr ail menus for every application within the on-screen kryboard. Instead. the directnrss associated with the menu selection through pointing with a mouse can be achieved by applying scanning to the menu where a command is selected when it is highlighted- Here. scanning selection matches the task of command selection. The natural arrangement of the menubar and individual menus. and consistent keystrokes to movr across items readily permits scanning to be applied. Since there is no object to move. a scanning menu approach similar to Strategy 4 offers the possibility to select any menu with a single on-screen kry. In this case. scanning would begin by displaying the lefi-most menu. Then rach menu would bç displayed lefi-to-right at scanning intemals (by repeating There are a number of complications that can anse with menu scaming. The first relates to canceling scanning. As observed with Strategy 4, the use of a cancel switch can leave an undesired system state. In the case of menus, the menu may be lefi visible. This may require a number of keystrokes to clear aftenvards. Thus. the on-screen keyboard must take the responsibiiity for ensuring that the cancel switch not only canceis the menu scanning. but puts away the menu. This can only be done by associating some special function with the cancel switch. In the case of the WiViK on-screen keyboard, it has been specifically programmed to interact with the application and restore it to the state prior to scaming the menus. rem ipsum dolor sit amt mlutpat Ut wsi enim ad mrnim veniam, quis nostrud exerc odo consequat lobortis nisl ut aliquip ex ea commodo consequat Duis autem vel eum mure dolor in hendrerit in vulp cor iat nulta facilisi. ' II consequat, vel illum dolore eu feugiat nulla facilis. iusto odio dignissim qui blandit praesent luptatumrl 1 Figure K-1:Scanning menus: Menus are displayed sequentially from left-to-right; selecting a menu starts scanning down menu items. If only a single select switch is available. canceling scanning menus requires underlying knowledge of the menus or a means to acquire that knowlrdge. In an on-screen keyboard. canceling is often associated with a certain number of wnparounds. This is accomplished by the on-screen keyboard being aware of its own dimensions and when wraparounds occur. If a repeating Another complication arises with hierarchical menus, as a fixed sequence of repeating keystrokes cannot be pia~edin advance. When a hierarchical menu item is highlighted, the user can move across to its submenu with a Figure K-2: Hierarchical menus are difficult to use a fixed sequence of actions to scan. In the case of long menus. therr is a similar problem as scaming across many words in a text field. and a means to move quickly through the menu is desinble. An overdrive function would be useful. However. since a second cancel switch is essential. a third overdrive switch may not be possible if the user is very physically limited. Stepping across menu items by some group size might be possible. but mon would likely occur as observed with Strategy 3 bbecause users would have difficulty knowing when to stop scaming without overshooting the desired item. Window View Scroll bars are typically used to quickly move through a document or window view. They are operated in a GUI with a mouse in several ways which complicates their use. especially if it was attempted through scanning mouse emulation. The user could click on the up or down scroll buttons to scroll by a small amount. or they could hold the scroll bunon down to repeatedly move by this small amount. The user could move by larger amounts with similar actions while pointing in the scroll bar above or below the scroll bar handle. Al1 of these actions normally rrquire good pointing and clicking andior holding skills with a pointing device. The task is actually much simpler -to scroll the view of the document up or down through small or large movements. From a task transparency viewpoint, this task can be interpreted as scrolling the window view or selecting the end window view. However. the latter view cannot be supported because the entire document cannot be viewed at one timr such that the desired view is directly selected. Scrolling the window view by scaming can be achieved with repeating messages to the scroll bar. This is difficult because scroll bars typically lack keyboard equivalents. However. scroll bars can respond to direct operating system messages. A special scroll function must be programmrd within the on-screen kryboard where it could be treated like a keystroke within a repeat loop to scan. Up and down scroll keys must be provided at one or two movement sizes. or sequenced from large to small. Similar keys must be provided for horizontal scrolling. The end rcsult is thnt the user views the rntire screen scrolling in scan steps (Figure K-3). Cancsling a scrolling operation has no negative sidr effects that must bc specially considered. accum~anet iusto odio ui blandit praesent iuptatum nnl delenit augue duis dulorê te Lorem ipsum dolor sit amet, consectetuer nibh euismod tincidunt ut I dolore magna aliquam erat volu Ut wisi enim ad minim quis nosbud exerci tabon ullamcorpi' suscipit lobortis nisl ut aliquip consequat ni IIC si ,tom irai ai im ini ira dninr in hnnArnnf in in ilni itata irnlit nccn mnlnchn . - & - -: , - - - . . , . , . r .A-,, '1% . k.4 - - " - ,_ + . . .. - - - .(r l _ . I v...."7 ,- . ...-. K.,- . . .-,. . ..-y,+, ,-?+&S.: s 2 .:"-....*-y ::i-. .- f%rHefp,press R .=. ' - ' .::]- - , .-- Ir. ,' . i - - . * - . -.. .rINucu(-~ Figure K-3: Scrolling a window: the view scans vertically or horizontally. The user stops the scanning when the desired view is displayed. The scroll bar handle movrs at the same time as an anifact of the GUI but the sca~ingview rernains the prime focus for the user because it is so dominant with respect to the small scroll bar handle. Although this is quite different from scanning an on-screen keyboard. it matches the task and user's viewpoint and is therefore direct. Window Size and Position Re-sizing a window's border is a task where the visual feedback of the moving border is critical to completing the task. Scanning must engage the border in its operation so that the user feels directly in control of the task. Again. this differs from the scanning mode1 of the on-screen kryboard but is entirely consistent with the user's view of the task. In this way the user sees the border scanninghesizing in a direction of their choice and stops it when i t reaches the desired size (Figure K-4). Since each border can move in two directions. a total of eight krys to initiate scanning in a desired direction must be provided in the on-screen keyboard. Using keystrokes. a window border can firsi be identified, then a repeat loop of an arrow step can resize that border. When the scanning stops. a keystroke (e.g.. accumsan et iusto odio dignissim qui blandit praesent luptatum znl delenit A augue dus dolore te feugait nulla facilisi Lorem ipsum dolor sit amet, consectetuer adipiscrng dit. sed diam nonummy nibh euismod tincidunt ut I dolore magna altquam erat volutpat Ut wisi enim ad minim veniam. quis nostrud exerci tabon ullamcorpç I/ suscipit lobortis nisl ut aliquip ex ea commodo consequat. ni tic 16+am rrol oi trn irri ira dAnr in handronl in rn tini th+a rralit occa rnnlacha 4 Figure K-4: Resizing window borders through scanning Similar scanning could be applied to moving a window. Here again. the scaminghoving window best matches the task (Figure K-5). Since resizing and rnoving windows take place with reference to the screen dimensions. the scaming must also work in those dimensions. In comparison to text scanning and even scrolling. thrre are no natural movement increments at the screen level. Therefore. an appropriate grid dimension must be set at the operating system level to correspond to the drsired distance a step key should move a window. v-.---l u a accurnsan et iusto odio dignissim qui blandit praesent tuptahim nnl lele iit A augue duis dolore te feugait nulla facilisi Lùrem ipsum dolor sit amet, consectetuer adipiscing dit, sed diam nunummy nibh euismod tinctdunt dûlore magna aliquam erat volutpat I Ut wisi enim ad minim veniarn. quis nosbud exerci tabon ullarnchc susci~itloborûs nisl ut aliaum ex ea commodo conseauat r~tII= 31ifam iioi ai lm tnt trn AAnr in kaodrnnf in >n ilni ttdn itnltt acco ?nlact!a 1( For Help. press Fl ' . ... -. Tm.& Figure K-5: Moving the window through scanning. Dialog Controls Dialog controls represent a dynamic set that Vary with every dialog box. Some particular controls appear in most dialogs such as the 'OK' and 'Cancel' buttons and shouid be included in the on- scrern keyboard as selection shortcuts. Other controls should be scanned across. Dialog boxes ofien have a consistent set of keystrokes to move focus fiom one control to another which can be used to apply this scaming. If a dialog follows common design guidelines, then scaming movement will appear as logical item scanning. If the button order was not considered in advance. then sca~ingwouid appear haphazard. There are also ofien groups of controls within a dialog box, analogous to hierarchicai menus that are scanned first. Here, the access system must be able to srnse such grooupps to allow for appropriate scaming within a control group. Since standard keystrokes to move across controls do not distinguish between particular types of controls. a sequence of keystrokes to complete a task in a single operation cannot bc plannrd in advance. Once a control is in focus. the user may be faced with a nurnber of choices (Figure K-6) such as selecting a control and entering text (O). moving down or up and choosing fiom a list of items (@) toggling a control with a Figure K-6: Scanning across varying dialog control objects; each reguiring different actions. An immediately apparent problem is that as focus scans fiom object to object, the focus indicator is often difficult to discrrn as in Figure K-7. Ideally, some more visually apparent feedback should be available. r .FaM Wafd Fo-ms . . . : - - 2 - - - - .' .".& Figure K-7: Focus indicator scans from object to object, but is ofien difficult ::V1flt3t Cvnluni lulu TEST TARGET (QA-3) APPLIED IWGE . lnc E 1653 East Main Street -.I --, Rochester. NY 146û9 USA ---- Phone: 716/48Z!-OXKl ------Fax: 71Wôô-5989 0 1993. Appiied Image. lm.. Ail Rights Reserred