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Peering Inside the Operators' Toolbox

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Peering Inside the Operators' Toolbox FINISWG THE DFcIGN: PEERING INSIDE THE OPERATORS' TOOLBOX Gemrd L. Torenvliet A thesis submitted in conformity with the requirements for the degree of Master of Applied Science Graduate Department of Mechanical & Indusuial Engineering University of Toronto O Gerard L. Torenvliet (1999) National Library Bibliothèque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. ma WellMgton OîîawaON KlAW OaawaO(J K1AW Canada Canada The author has granted a non- L'auteur a accordé melicence non exclusive Licence aiiowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distriiuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conseme la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ..hstead of searching for mechanisms in the environrnent that tum organisms into trivial machines, we have to find the mechanism within the organisms that enable thern tu tztrn their environment into a rrivial machine. Finishing the Design 1 Torenvliet, Gerard Lawrens (1999). Finishine the desi-gn: Peering; inside the operators' toolbox. Master's Thesis, Graduate Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, CANADA. ABSTRACT While interacting with complex systems, operators of these systems fiequentIy modify their interfaces in order to achieve task goals more effectively or more efficiently (what Rasmussen (1986) has called 'finishing the design). While there is a literature on operator modifications, this literature includes only field studies and theoretical treatments, but has not proceeded to experimentation. This research describes two prelirninary experiments designed to answer four questions related to operator modifications: (1) Why do operators modify their interfaces? (2) How do these modifications develop over time? (3) How does this activity affect performance? and (4) How does this activity affect understanding? The resuits of these experiments pointed to answers to most of these questions, and most significantly, pointed to a taxonomy of the purposes behind operator modifications in complex systems. .. Finishinz the Design II ACKNOWZEDGMENTS This research was supported by grants from the Naniral Sciences and Engineering Research Council of Canada and the Japan Atomic Energy Research Institute (Dr. Fwniya Tanabe, contract monitor). A number of people were instrumental in cornpleting this research. First thanks go to my supervisor, Dr. Kim Vicente, for supporting and guiding this research effort. Deeper than that, 1 would Iike to thank Kim both for introducing me to the field of cognitive engineering during my undergraduate education, for fostering my enthusiasm in the field, for putting up with my weaknesses. and for developing my research career. Thanks are also due to Dr. Cathy Burns. who hris helped me tu flesh out a number of the ideas presented in this thesis, and who has helped me out with other research leading up to this thesis. John Hajdukiewicz also deserves mention for putting up with my barging into his off~ceto unload some new idea or insight. and for encouraging me in my work. Finally, this thesis is dedicated to three important individuals: to my father who sparked my love of science. to my mother, who has nurtured it, and to my wife, who has penevered with it. 1 have been blessed to have each of you in my life. To the glory of God done. G.T., July 1999 Finishing the Design iii TABLE OF CONTENTS Abstract ............................................................................................................................................ i .. Acknowledgments ...........................................................................................................................11 ... Table of Contents ........................................................................................................................... 111 Table of Tables ........................................................................................................ ... .................... vi Table of Figures .............................................................................. ... ............................................. ix Introduction ..................................................................................................................................... 1 Bac kground and Motivation ............................................................................................................4 Generd Theoreticai Treatments of Tool Use ....................................................................... 4 Moving From Theory to the Field........................................................................................ 8 Field Studies of Tool Use .................................................................................................... -9 Motivation: Moving From the Field to the Laboratory ...................................................... 15 Research Context ............................................................................................................... 18 Pilot Study ..................... ..,..... ................................................................................................... 19 Purpose ............................................................................................................................... 19 Experimental Design ...................................................................................................... L9 Participants ......................................................................................................................... 19 Apparatus ........................................................................................................................... 21 Procedure ............................................................................................................................ 22 Data Sources ....................................................................................................................... 25 Results: Tool Use ............................................................ .... ......................... 26 Results: Control Recipes .................................................................................................... 35 Results: Normal Tnal Completion Time ................. ...... .......... ............................... 39 Results: Normal Triai Blowups .......................................................................................... 42 Finishing the Design Results: Fault trials ............................................................................................................. 43 Discussion: Implications for a more thorough study ......................................................... 45 Experiment .................................................................................................................................... 47 Purpose ............................................................................................................................... 47 Experimental Design ............... ... ........................................................................................ 47 Participants ......................................................................................................................... 49 Apparatus ........................................................................................................................... 52 Procedure ............................................................................................................................ 52 Data Sources....................................................................................................................... 54 Results: Tool Use ............................................................................................................... 54 Results: Normal Trials ....................................................................................................... 87 Results: Fault Trials ..................................................................................................... 97 Results: Control Recipes .................................................................................................... 97 Results - Abstraction Hierarchy Analyses ................................................................ 98 Discussion ................................................................................................................................... 101 Why do operators modify their interfaces? .................... ,.. ......................................... 101 How do operator modifications develop over time? ....................... ... ......................... 104 Do operator modifications affect task performance? ....................................................... 105 Do operator modifications affect understanding? ............................................................ 105 ConcIusions ................................................................................................................................
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