Design and Evaluation of Dynamic Text-Editing Methods Using Foot Pedals

ARTICLE IN PRESS

International Journal of Industrial Ergonomics xxx (2008) 1–8

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International Journal of Industrial Ergonomics

journal homepage: www.elsevier.com/locate/ergon

Design and evaluation of dynamic text-editing methods using foot pedals

Sang-Hwan Kim, David B. Kaber*

Edward P. Fitts Department of Industrial and Systems Engineering, North Carolina State University, 111 Lampe Dr., 438 Daniels Hall, Raleigh, NC 27695-7906, USA article info abstract

Article history: The objective of this study was to design and evaluate new dynamic text-editing methods (chatting, instant Received 11 February 2008 messenger) using a foot pedal control. A first experiment was to assess whether the foot-based method Received in revised form 30 June 2008 enhanced editing performance compared to conventional mouse use and to identify which type of foot Accepted 15 July 2008 control is most convenient for users. Five prototype methods including four new methods (two pedals or Available online xxx one pedal, 0 order or 1st order control), and one mouse method were developed and tested by performing a task requiring changing text sizes, dynamically. Results revealed methods involving 1st order pedal control Keywords: to be comparable to the conventional method in task completion time, accuracy and subjective workload. Foot pedals Text editing Among the four foot control prototypes, two pedals with 1st order control was superior to in performance. A Control systems second experiment was conducted to test another prototype foot-based method for controlling font face, size, and color through feature selection with the left pedal and level selection with the right pedal. Text- editing performance was compared to conventional mouse-based editing. Results showed the foot pedals to degrade performance in terms of task completion time. However, the prototype interface has the advantage of making certain system functionality accessible to special populations that might not otherwise be able to use dynamic text-editing applications. Subjective comments demonstrated the foot pedal methods to be considered useful, time efficient and to reduce workload. It was observed that skilled users might perceive some relief from cumbersome mouse handling behaviors during typing. Although the foot pedal control was not revealed to significantly increase text-editing performance over conventional mousing, the use of foot pedals may be considered in computing operations, including dynamic text-editing tasks, as an alternative or additional input method, particularly for special populations. Relevance to industry: The development and evaluation of foot control interaction methods for text editing may provide useful insight for human-computer system designers considering the use of additional input devices or ways to support user expressions of emotion in text. The foot control approach may also be useful in interaction design for special populations (with functional limitations of the upper limbs) in terms of accessibility. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction research has shown the feet are slower and less accurate than the hands (Kroemer, 1971), and foot controls often restrict user posture. 1.1. Foot controls Having to maintain a foot on a control makes it more difficult to shift posture in a seat or change the position of the legs, for example. As the computer has become a common tool in the work envi- Operating foot controls from a standing position also requires people ronment,functionsusedbyhumanshavebecomemoreandmore to balance their weight on one foot at a time. Despite these issues, foot complicated and require various types of interaction. This has led to controls have continued to have a place in control tasks (see Sanders development and use of hand-control input devices such as and McCormick (1993: Chapter 11) for other examples). Several keyboards, mice, trackballs and joysticks. Human foot control devices research studies have been conducted to identify design parameters are also essential to modern life including working with vehicles. In affecting performance with foot controls. Ayoub and Trombley (1967) order to use a foot to control a system, pedals have been designed and investigated travel time in pedal movement with various fulcrum developed for specific tasks (e.g., pedals for aircraft rudder control). locations, and Drury (1975) developed a modified version of Fitt’s law However, hand controls are, far and away, more widely employed for to predict movement time in moving a foot from one pedal to another machine control. One reason for this is that prior human factors’ pedal. This work has been used as a basis for effective pedal design in, for example, automobiles (Morrison et al., 1986). * Corresponding author. Tel.: þ1 919 515 3086; fax: þ1 919 515 5281. The most commonly used foot controls are the brake and accel- E-mail address: [email protected] (D.B. Kaber). erator pedal controls of automobiles. People who do not have

Please cite this article in press as: Kim, S.-H., David B. Kaber, Design and evaluation of dynamic text-editing methods using foot pedals, International Journal of Industrial Ergonomics (2008), doi:10.1016/j.ergon.2008.07.010 ARTICLE IN PRESS

2 S.-H. Kim, D.B. Kaber / International Journal of Industrial Ergonomics xxx (2008) 1–8 functional limitations in foot and cognitive activities make contin- use menu in the Kinedit tool. With this in mind, we hypothesized uous use of foot control pedals in driving a car without distinctive that use of foot controls to allow the hand to remain on a keyboard difficulties. Foot pedals are also used frequently with musical while the feet are used to adjust text properties in a dynamic tex- instruments including pianos, electric guitars, organs and drums, and t-editing application such as chatting and instant messenger would in other mechanical equipment including, cranes, sewing machines also serve to promote application effectiveness. and industrial controls. On this basis, it may be advantageous to incorporate foot controls in human–computer interaction tasks (Dix 1.3. Research objective et al., 2004). Some researchers have investigated the use of foot pedals with desktop computing applications. Mohamed and Fels At this time, there are no common foot pedal devices and (2002a,b) invented and introduced a system for controlling music applications for desktop computing. The functionality of prototype sequencing software from a piano keyboard and by adding a foot devices has been limited to the foot pedal being used for simple, switch. The system eliminated the need for a computer keyboard and discrete or binary selection of modes of system operation and not mouse by relocating their functions to the piano keyboard, and the for continuous control. The objective of this study was to investi- foot switch was used as a mode control to distinguish between gate whether a new methodology for text editing, using a foot keystrokes representing notes and macros. An experiment was control pedal with continuous control, is accessible and acceptable conducted to compare the two methods of conventional computer to users for dynamic text-editing performance involving frequent/ keyboard use and the new piano controls. They found the foot pedal dynamic typeface changes. A first experiment was conducted to to be effective for preventing mode errors. Sellen et al. (1992) identify which type of foot control (using two pedals vs. one pedal, examined the effectiveness of a foot pedal to present kinesthetic using a 0 order or 1st order control system) most convenient for feedback to users and prevent mode errors in a text-editing task setting text size in document editing. In addition to this, the through two experiments. Results showed the foot pedal feedback to method for setting a specific property of text using the foot pedal be successful and to reduce cognitive load. Both of the studies was compared to mouse-based editing methods for the same task. mentioned above considered foot pedals as devices to select discrete In a second experiment, we tested another prototype, which was modes of control. Of course foot pedals can also be used for designed to control the font face, size, and color through mode controlling continuous properties, like a gas pedal in an automobile. selection with the left foot pedal while using the right foot pedal for setting each property. Performance using this prototype was also 1.2. Typography and kinetic text compared to a mouse-based method of editing.

Text editing is one of the most dominant tasks in computing 2. Experiment 1 operations. In office environment, many workers see and edit text material displayed on a screen through computers. In spite of the Because current editing methods involving a mouse may require extensive use of interfaces for text editing, the vast majority of frequent hand repositioning to select a specific text property, in this applications are less effective than they could be. In order to experiment we hypothesized that the new foot control prototype enhance the visualization effectiveness of text information, some would produce significant reductions in text-editing time, errors studies have examined typography in displays. Typography was and perceived workload. We also expected that the action of a single first considered for providing implicit information beyond external pedal would require lower workload than the action of using two properties. Mackiewicz and Moeller (2004) demonstrated that pedals due to repositioning of the foot. Finally, the 1st order control every typeface has a different ‘‘personality,’’ or the ability to convey was expected to be more convenient for the user in setting specific different feelings and moods. They conducted an experiment levels of font size. Because foot control is limited for fine manipu- analyzing participant ratings of typefaces for different personality lation, the selection of text properties by pressing a pedal to attributes and investigated why participants rated typefaces high a specific position (0 order) was expected to be more difficult than or low on particular personality attributes. setting properties by increasing or decreasing speed of, for example, Dynamic text information has also been considered for text size changes through pedal position (1st order). extending the use and effectiveness of text-editing applications (e.g., chatting, instant messenger). Ford et al. (1997) introduced 2.1. Method ‘‘kinetic typography’’ as a new method for displaying text that takes advantage of the dynamic nature of digital media. The authors 2.1.1. Prototypes expected kinetic typography of text to be effective in conveying A Java-based text-editing application was developed for the a speaker’s tone of voice, qualities of character, and affective experiment and used to assess foot control prototype usability and qualities of text. Related to this, they demonstrated that changing performance. The text editor had similar functions to Windows a few variables of text (e.g., font size or font color) may be enough to WordPad and was akin to interfaces used for on-line chatting or IM present user feeling. Forlizzi et al. (2003) pointed out that kinetic (e.g., AOL, MSN messenger). The interface is presented in Fig. 1.In text-editing application may require many steps for users to modify the tool bar, there are icons for file management (open and save), dynamic text properties. They presented the ‘‘Kinedit’’ system as editing (cut, copy and paste), and modifying text styles (bold, italic a basic authoring tool which allowed for exploration of the and underline). There are also three combo boxes for selecting text communicative potential of kinetic typography (dynamic text) for properties, such as font face, font size and font color. personal communication. The concept of using kinetic typography In order to utilize foot pedals for setting font size, a commercial was applied to specific communicative applications, such as an foot pedal device (Logitech Wingman), including a ‘‘gas’’ and email system (Uekita et al., 2000) and an IM (instant messenger) ‘‘brake’’ pedals, was integrated with the text editor (see Fig. 2). (Bodine and Pignol, 2003) to determine whether users could There were four different methodologies for using the foot control effectively express emotion through a dynamic motion grammar of pedals, including two pedal counts by two orders of control. text. Although effective for this purpose, the applications of this For changing text size, when editing using two-foot pedals, the concept had limitations since there was ‘‘dynamic text but non- ‘‘gas’’ pedal on the right side of the input device was used for increasing dynamic editing interfaces.’’ To change simple text properties (e.g., font size and the ‘‘brake’’ pedal on the left side was used to decrease the font size) in various ways while typing, a user has to make text size. (The default text size was set to 12 point in all trials.) This cumbersome hand movements between a keyboard and a mouse to method of editing was explored under the two orders of control.

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B 1st order control system: pressing the pedal determined the rate of increase in the text size, regardless of the specific depth of the pedal, and releasing it fixed the text size at the present setting. A full press of the pedal (‘‘to the floor’’) and release reset the font size to the default.

In order to present feedback to a user while pressing a pedal to change text size, the color of the combo box showing the current text size changed from ‘‘white’’ to ‘‘yellow’’ and the number in the combo box increased or decreased dynamically. In addition to the four editing methods using foot pedals, a conventional mouse method was evaluated to compare performance. Thus, in this experiment, each subject was required to use ﬁve editing methods for setting text size. The order of presentation of the prototype methods was randomly assigned for each subject to reduce potential order and learning effects in performance.

2.1.2. Tasks Fig. 1. Java-based text editor. Subjects were to prepare short text documents including various font sizes, like typing an emotional message in a chat B 0 order control system (sustained pedal position): the session. All subjects were provided with a practice and test trial depressed position of a pedal was designed to represent a text with each control interface. The document for the practice session size. If a user wanted to maintain a specific text size, (s)he held consisted of 66 words, including 38 words (58%) of default size (12 the gas or brake pedal at the specific position. point), and required 15 text size changes. The document for the B 1st order control system (latching pedal): pressing a pedal experiment session consisted of 102 words, including 48 words determined the rate of increase or decrease in text size, like (47%) of default size (12 point), and required 20 text size changes. control with the accelerator or brake pedals in a car. The same task documents for practice and testing were used across all editing methods. In the case of using a single foot pedal to change text size, only Since it was not possible to select a block of text to change the gas pedal was designed to be used. In order to set a specific text properties after typing by using the foot pedals, subjects were not size, a user pressed the pedal to increase the value, and then allowed to select a block of text in trials using the mouse for this released the pedal to fix the font size. When the pedal was pressed purpose. They used the mouse to choose an appropriate icon or ‘‘to the floor’’ and released, the text size was reset to the default size level in the combo box before typing the required text. This is, (12 point). This method of editing was also explored under two however, the approach most professional typists use in document orders of control. reproduction (i.e., toggling on ‘‘bold’’ or ‘‘underline’’ prior to typing and then toggling it off) vs. typing the text, selecting it with the B 0 order control system: the pressed position of the pedal rep- mouse and then manipulating the text property. Each subject used resented the text size, but the text size would not decrease if the five editing methods for setting text size. The order of the pedal was released. If a user wanted to decrease the text presentation of the methods was randomized for each subject to size, the pedal had to be pressed ‘‘to the floor’’ and released, reduce potential order and learning effects in the analysis. then the user pressed the pedal again to set the text size. 2.1.3. Subjects Ten participants were recruited for the experiment. The volun- teers were required to have PC experience, including text editing, email, or chatting using the English language. They were also required to have experience in driving a car without any physical or mental limitations and using the control pedals. Participants ranged in age from 18 to 35 with a mean of 26.5 years. Eight were male and two were female. They were compensated for their participation with a $5 gift certificate. As part of the procedures, subjects were asked to complete a survey (prior to any training or testing) in order to establish the general characteristics of the sample population. On a scale ranging from 1 (none) to 5 (frequent), subjects reported an average rating of 4.6 for general PC experience (sd ¼ 0.66), a rating of 4.4 for document experience (sd ¼ 0.49), a rating of 3.8 for chatting or IM application experience (sd ¼ 0.87), and a rating of 4.1 (sd ¼ 0.7) for experience in vehicle driving. This indicated substantial subject PC and driving experience.

2.1.4. Variables and measurement The independent variable for this experiment was the type of editing method. The method encoded the number of pedals (one vs. two) and the order of control (0 vs. 1st order). The mouse method represented a control condition. The dependent variables included Fig. 2. Foot control pedal. time-to-document completion (TDC), number of errors, subjective

4 S.-H. Kim, D.B. Kaber / International Journal of Industrial Ergonomics xxx (2008) 1–8 workload, and user subjective satisfaction ratings. Subjects were Task Completion Time instructed to type the documents as fast as possible, as in an intense 400 chat session. Errors were deﬁned as a failure to set the required text 350 size and typing with an incorrect text size. (Simple typing mistakes 300 (e.g., misspelling) were not counted as errors.) Therefore, the subject was also instructed to attempt to limit the number of errors 250 as much as possible. The NASA-TLX (Task Load Index) scale was 200 used to measure subjective workload during test trials. The demand 150 280.5 264.3 283.1 273.6 273.6 ranking form was completed by subjects after the ﬁrst practice trial 100 by each subject and the rating form was completed after each test Time-to-task (sec) 50 trial. A rank-weighted sum of ratings was calculated for each 0 control interface type. Along with the NASA-TLX, a post-trial 2 pedals, 2 pedals, 1 pedal, 1 pedal, conventional questionnaire on subjective satisfaction ratings and opinions on the 0 order 1st order 0 order 1st order method prototype methods was administered. Methods

Fig. 3. Task completion time (in s) for five different editing methods. 2.1.5. Experimental design and procedures The experiment followed a completely within-subjects design. Participants completed one test trial with each editing method. This result was counter to one of our expectations that using There were a total of 50 trials across all subjects (10 subjects 5 a single pedal may be more convenient for users than using two trials). The experiment began with an introduction and equipment pedals. It can be inferred from this result that users don’t have familiarization period. An informed consent was reviewed and difficulty in using two pedals, which may be due to experience in signed by the subjects. Subjects then practiced and tested with repositioning their feet among multiple pedals in driving a car in a prototype. Each trial with each prototype lasted approximately every day life. 5 min. After each test trial, subjects were asked to complete the workload evaluation sheet (NASA-TLX) and subjective satisfaction 2.2.2. Number of errors questionnaire. Because of the limited number of errors observed in trials, a non-parametric (Kruskal–Wallis) test was used to assess an effect 2.2. Results of experiment 1 of editing method on number of errors, and it proved to be 2 significant (c 4 ¼ 33.1903, p < 0.0001). The prototype method 2.2.1. Time-to-document completion involving two-foot pedals with 0 order control induced more errors Since there were individual differences in typing skills (e.g., than all other methods. There were no significant differences typing speed) between subjects in the sample, all TDC data was between the other methods (see Fig. 5). Similar to the TDC results, normalized to provide a consistent mechanism for interpreting even though the use of the foot pedals did not produce better results. TDC data was converted to standardized (z) scores for each performance than the mouse method, all foot methods except two subject across the five prototype methods; that is, all TDC obser- pedals with 0 order control were comparable to the mouse method. vations for each subject were expressed as a statistical distance For the four pedal methods, A Kruskal–Wallis test also revealed from the mean TDC for that subject. Graphical analysis and diag- 2 the effect of order of control to be significant (c 1 ¼19.8211, nostic tests on residuals for a model of TDC in editing methods p < 0.0001) on errors. Prototype methods with 0 order control revealed no ceiling or floor effects and that the data confirmed with induced more errors than methods with 1st order control. This was a normal distribution. In general, there were two analyses on each in-line with our expectation. However, the same test on the effect of response measure. The first analysis was a one-way comparison number of pedals revealed errors to be significantly greater when (e.g., ANOVA for TDC and workload) of the five prototype methods 2 using two pedals vs. a single pedal (c 1 ¼3.8874, p < 0.0487). Fig. 6 including the four pedal methods and conventional mousing illustrates the effect of the two factors on errors. We inferred users method. The second analysis used a two-way ANOVA to compare might have difficulty in maintaining specific depressed pedal posi- the four pedal methods in terms of the number of pedals and the tions to set specific text sizes while typing text with a keyboard. control order. Each factor had two levels and the analysis excluded Interestingly, regardless of the number of pedals used, foot pedal the conventional mousing method. Analysis of variance (ANOVA) results revealed average task time to not differ among the five methods (F4,45 ¼ 1.34, p ¼ 0.2702). This 285 result suggests use of foot pedals for controlling text size in dynamic text editing produces performance comparable to 280 mousing; however, performance with foot pedals was not better than the mouse, for the specific application. Fig. 3 presents the 275 actual task time for each prototype method. In order to identify which type of foot action (two pedals vs. one, 270 and 0 vs. 1st order control) yielded better performance in terms of speed, a two-way ANOVA was performed on the data for the four 265

pedal methods (excluding the conventional mousing method). Time-to-task Results revealed no significant interaction effect between the 260 number of pedals and the order of control. There was also no 0 order significant difference in task time between the 0 and 1st order 255 1st order control (F1,38 ¼ 1.55, p ¼ 0.2201). However, there was a marginally 250 significant difference between the use of two pedals vs. a single 2 pedals 1 pedal pedal (F 3.05, p 0.08). The use of single pedal for setting text 1,38 ¼ ¼ Number of pedal size produced longer performance times. Fig. 4 presents the task completion time by the number of pedals and the order of control. Fig. 4. Task completion time for types of foot control.

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Number of Errors Subjective Workload (NASA-TLX Rating) 8 100 7 6 5 80 4 3.7 3 60

(Observed) 2 0.6 40 Number of Errors 1 0.1 0 0 Workload 0 63.84 62.13 56.28 57.21 51.74 2 pedals, 2 pedals, 1 pedal, 1 pedal, conventional 20 0 order 1st order 0 order 1st order method Methods 0 2 pedals, 2 pedals, 1 pedal, 1 pedal, conventional Fig. 5. Number of observed errors in using five different editing methods. 0 order 1st order 0 order 1st order method Methods methods with 1st order control yielded 0 text setting errors. Thus, even though the results revealed the use of two pedals to be poor for Fig. 7. Workload ratings for five different editing methods. accuracy, a method adopting 1st order control may effectively be used for similar types of tasks. (A formal analysis of the interaction of 2.2.4. Post-experiment questionnaire the pedal count and control order was not possible because of the Questionnaire responses were averaged across all 10 subjects. non-normal data and limitations of the non-parametric test.) The first question asked subject to rate the usefulness of the prototype, on a scale of 1–7 (where 1 ¼ ‘‘not useful at all’’ and 2.2.3. Subjective workload 7 ¼ ‘‘extremely useful’’). A Kruskal–Wallis test revealed no signifi- An ANOVA was performed on standardized subjective workload cant differences among the four methods using the foot pedals. scores, which were calculated to account for individual differences Table 1 presents the range and mean values of subject responses. In in internal scaling of workload responses. Results revealed average general, all prototype methods were rated over 4, and text size workload ratings for the five editing methods to be significantly setting using the foot pedals was considered ‘‘fair.’’ different (F ¼ 2.75, p ¼ 0.0396). Fig. 7 shows the mean subjective 4,45 To the second question asked whether the prototype method workload by methods. Tukey’s multiple comparison test revealed saved text-editing time, compared to the mouse method. Over 50% two groups: one including the four foot methods; and another of subjects answered ‘‘Yes’’ for the two pedal methods and over 50% group consisting of the two methods using foot pedals with 1st responded ‘‘No’’ for the single pedal prototypes. These opinions are order control and the mouse method. These results suggest use of in-line with the performance and workload results. The last ques- a foot pedal with a 1st order control is comparable to the use of tion asked whether the prototypes reduced workload. Subjects a mouse in terms of workload. were neutral with respect to using two pedals and reported In order to determine which type of foot control to higher increases in using one pedal. workload, a two-way ANOVA was performed on the TLX scores for From an additional analysis of subject comments, the major the four pedal methods. Results revealed no significant interaction reason why foot methods were assessed as being useful was effect between the number of pedals and the order of control. elimination of the requirement to move a hand between a mouse Results also revealed workload ratings to be consistent across the and the keyboard. Subjects said this allowed them to keep number of pedals (F ¼ 0.01, p ¼ 0.9415). However, there was 1,38 concentrating on typing. Opposite to this, subjects felt the proto- a marginally significant difference among foot methods using 0 and type method using two pedals with a 0 control order system was 1st order control (F ¼ 3.72, p ¼ 0.0618). The use of pedals with 1,38 difficult to use due to the need to press the foot pedals to a specific 1st order control required less workload and this was in-line with position to fix font size. Regarding the prototype using two pedals our expectation. Fig. 8 shows the workload ratings by the two with a 1st control order, subjects observed that they had to wait independent factors. until a desired text size was reached while pressing the foot pedal. Concerning the editing methods using a single foot pedal, for both

2 pedals 3.5 66.0 1 pedal 2 pedals 3 64.0 1 pedal 2.5 62.0

2 60.0

1.5 58.0 Workload Number of Errors 1 56.0

0.5 54.0

0 52.0 0 order 1st order 0 order 1st order Control order Control Order

Fig. 6. Number of errors for types of foot control. Fig. 8. Workload ratings for types of foot control.

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Table 1 text-editing tasks, including reducing TDC and number of errors, Results of subjective survey for experiment 1 as compared to mouse-based editing, requiring additional hand Input method Using 2 pedals Using 1 pedal movement. The foot method was also expected to reduce

0 order 1st order 0 order 1st order perceived workload and promote subject satisfaction with performance. Usefulness (1 ¼ no–7 ¼ useful) Range 2–7 4–7 1–7 1–7 Mean 4.6 5.2 4.1 4.5

Time saving Yes 5 6 2 4 3.1. Method No 3 3 7 5 Don’t know 2 1 1 1 3.1.1. Prototypes Workload reducing Yes 4 4 3 2 The Java-based text-editing application used in the first exper- No 5 4 7 6 iment was also used in this experiment. The brake pedal was used Don’t know 1 2 0 2 to set the text feature mode. If a user pressed the pedal, the focus of the system on the available combo boxes changed iteratively in the order of font face, size and color. Feedback included a change in the 0 order and 1st order control, subjects said they did not like color of the combo boxes from gray to cyan. After a user selected resetting and repeating text sizing when the current text size was a mode, (s)he selected a specific setting of a font characteristic with larger than the desired text size. the gas pedal. In the combo box for font face, 10 types of fonts were included and sorted by alphabetical order from ‘‘Arial’’ to ‘‘Ver- 2.3. Discussion of experiment 1 dana.’’ The combo box for setting text color included five color labels sorted alphabetically from ‘‘Black’’ to ‘‘Red.’’ The use of the Results demonstrated that certain foot control methods pedal for selecting feature levels was identical to that of using the (involving 1st order control) for dynamic text editing produced single pedal method with 1st order control in the first experiment. comparable performance, including speed, accuracy and subjective We selected this method since results revealed that 1st order workload, to the conventional mouse method. However, our control to be superior in terms of performance. Pressing the gas expectation that text editing with foot controls would enhance pedal increased the level of a selected text property (font face, size, performance was not supported. The use of foot pedals with and color) continuously, regardless of the specific depth of the desktop computing applications may require more training or pedal, and releasing the pedal fixed the text property at the dis- adaptation, even for users who are experienced in operating foot played level. A full press of the pedal and release reset the level of pedals in other contexts. Related to this, some subjects said more the selected text property to the default. (The default font face was time may be needed to develop skill in the use of foot pedals for the ‘‘Arial,’’ ‘‘12 point’’ for font size, and ‘‘Black’’ for font color.) As in the editing task, even after initial training. Beyond this, our results may first experiment, subjects were not allowed to use the mouse to reflect the general human performance finding that the feet are select a block of text to change properties after they had typed text. slower and less accurate than the hands for control task. They had to use the mouse to choose an appropriate level in the The experiment confirmed foot methods with 1st order control combo box before typing text. were easier to use, producing fewer errors and requiring lower workload than 0 order control. Subject comments confirmed that 3.1.2. Tasks selection of text properties by pressing a pedal to a specific position The practice and test documents differed from those used in the was more difficult than setting properties by using increasing or first experiment in that they included various font sizes, faces, and decreasing speed, due to the limitation of foot control in fine colors. The document for the practice session consisted of 72 words manipulation. Another contrast between the 0 and 1st order and required 14 changes in text properties. The document for the control methods is economy of movement and space. With 1st test session consisted of 112 words and required 26 changes in text order control, any change in output (e.g., text size) can eventually properties. be accomplished by displacing the control only a small amount. On the other hand, in 0 order control, larger output (position) changes 3.1.3. Subjects, variables, and procedures are accomplished by moving a linear control through a larger All 10 subjects who participated in the first experiment physical space (Wickens and Holland, 2000). Thus, if desired text continued their participation in the second experiment. All sizes in an editing application require wider range than those performance measures, procedures, and the experimental settings examined in this experiment, a 0 order control might require were identical to those used in the first experiment; however, only higher gain. two editing methods were compared, including the new foot pedal No prior research has assessed the impact of foot control design, and mouse control. in terms of pedals and order of control, on HCI application performance and perceived cognitive load. On the basis of these results, it 3.2. Results of experiment 2 can be recommended that the dynamic text-editing devices using two pedals with 1st order control be applied in text-editing task or 3.2.1. Time-to-document completion other comparable task environments as an alternative to mouse Graphical analysis and diagnostic tests on residuals for a model use. of TDC in editing methods revealed no ceiling or floor effects and that the data confirmed with a normal distribution. ANOVA results 3. Experiment 2 revealed average task completion time to be significantly different among the editing methods (F1,18 ¼ 10.9, p ¼ 0.004). Subjects were While the control methods used in the first experiment were slower in preparing the task document using the foot pedals than designed to change only text size, the method in this experiment using the mouse. The TDC means for the pedal and mouse editing allowed for setting several text properties, including font face, methods were 400.1 and 326.1 s, respectively (see Fig. 9). This size and color, with one foot pedal to select among features and result was counter to our expectation that the new foot method the other pedal to set the level of a feature. This method was also supporting mode changes would reduce dynamic text-editing time expected to enhance usability and performance in dynamic compared to mousing.

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Task Completion Time number of errors and subjective workload revealed the new foot 600 method to be comparable with the mouse method. It is possible the foot method led to added cognitive workload by requiring text 500 mode selection using the brake pedal. Subjects always conﬁrmed 400 the status of their mode selection using the visual display when- ever they tried to change text properties. This created an additional 300 attentional load at the very least. 200 400.1 After the second experiment, some subjects suggested it would 326.1 be convenient to integrate another pedal, or to use hot keys, for text

Time-to-task (sec) 100 mode selection and to use two pedals for increasing or decreasing 0 property values, like the method of using two pedals with 1st order Using Pedals Using Mouse control in the ﬁrst experiment. Finally, as in experiment 1, subjects Methods seemed to need more training to be skilled with using the foot method. Fig. 9. Task completion time (in s) for two text-editing methods.

3.2.2. Number of errors 4. Conclusion Results of a Kruskal–Wallis test for the effect of text-editing 2 methods on the number of errors was not significant (c 1 ¼ 2.2249, 4.1. General inferences p ¼ 0.1358). In this study, dynamic text editing using foot pedals for setting 3.2.3. Subjective workload text properties was examined. The experiments demonstrated Results of an ANOVA revealed no significant difference in a pedal method with 1st order control was comparable to mouse subjective workload between the two methods of text editing performance. Furthermore foot control configuration with two (F1,18 ¼ 0.54, p ¼ 0.4714). This was also counter to our expectation pedals and 1st order control was superior to all other methods. for the new method, but it suggested the foot pedals may induce A dynamic text-editing method using two-foot pedals, one for workload comparable to using a mouse. The average workload selecting the text control mode and another for controlling the level ratings for the foot peal and mouse were 61 and 56, respectively. of the selected text property, proved to be less efficient than mousing; however, subjective assessments revealed users to 3.2.4. Post-experiment questionnaire perceive the foot pedals as being potentially useful. In general, this Regarding the first question on the usefulness of each method, study demonstrated input methods using foot pedals can be the average rating (4.2) was the same for both methods (see applied to continuous control of object properties in desktop Table 2). This rating can be interpreted as ‘‘fair.’’ The result indicates computing applications, which goes beyond selecting simple use of foot pedals supporting functions for selecting text property control modes, as demonstrated in previous research. modes and for manipulating selected property levels may be comparable to using a mouse. 4.2. Caveats and future research Four subjects said the pedals allowed for time savings; however, none of the subjects said the mouse reduced task time, seven subjects One caveat of this study is that we did not investigate a text- were negative on use of the mouse for dynamic text editing. These editing method integrating a foot pedal and mouse. It was expected responses were not in-line with the TDC results, as performance that subjects might predominantly use the mouse as a result of using the foot pedals was significantly slower. Related to this, prior experience. Another limitation of this study was that subjects although there was no significant difference inTLX scores for the two- were not allowed to use a mouse to select a block of text to change editing methods, participants were more optimistic in the use of the text size, simultaneously. However, such action (selecting text) foot pedals for reducing subjective workload. Some subject said if the might be a typical behavior for some users in editing applications. foot pedal design were refined and additional training was provided, Finally, the task used in this research required subjects to reproduce they might prefer such a device over a mouse for text editing. a prepared document, including text properties (e.g., text size). Other text-editing tasks may have a different context, requiring 3.3. Discussion of experiment 2 different use of foot pedal controls. In regard to future research, it would be interesting to investi- The dual-function foot pedal editing interface did not produce gate the interaction of methods including both a foot pedal and an advantage over using a mouse in task time. The results on mouse. Such methods may make it possible to examine the behavior of selecting text blocks and associated text property Table 2 manipulation. Second, if foot pedal control is used in text editing, it Results of subjective survey for experiment 2 would be interesting to apply it for specific users and contexts. For Using pedals Using a mouse example, persons with functional limitations, such as the loss of Usefulness (1 ¼ no–7 ¼ useful) a hand or hands, might be able to use a voice recognition system for Range 2–7 2–7 text input and the foot pedals for dynamically modifying charac- Mean 4.2 4.2 teristics of text in a chatting or word processing application. Third, Time saving it would also be interesting to use other types of foot control Yes 4 0 devices (e.g., rudder pedals from an aircraft cockpit or a touch pad No 6 7 interface) and to attempt to match each device with appropriate Don’t know 0 3 types of tasks for enhancing human performance in interacting Workload reducing with computer systems. Lastly, we would like to search other Yes 4 1 domains and associated functions to utilize the foot control inter- No 6 7 face; for instance, zooming in/out in a CAD or map application, or Don’t know 0 2 3D navigation in a virtual world.

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