DEPTH PERCEPTION IN REAL AND VIRTUAL ENVIRONMENTS: AN EXPLORATION OF INDIVIDUAL DIFFERENCES Caitlin Akai B.A, University of British Columbia, 1998 A THESIS SVBkIITTED IN PARTIAL FULFILLhlENT OF TIiE REQUIREMENTS FOR THE DEGREE OF MASTEROF SCIENCE in the School of Interactive Arts & Technology @ Caitlin hkai 2007 SIMON FRASER UNIVERSITY Summer 2007 All rights reserved. This work may not be reproduced in hole or in part. by photocopy or ot,ller means. witJwut the pernzission of the author. APPROVAL Name: Caitlin Akai Degree: Master of Science Title of thesis: Depth perception in real and virtual environments: An es- ploration of individual differences Examining Commit tee: Dr. Halil Erhan, Chair Dr. Brian Fisher, Senior Supervisor Dr. Stcve DiPwola, Supervisor Dr. .John Dill: Supervisor Dr. Vince Di Lollo, Esterilnl Examiner, Adjunct Professor, Depart,ment of Psychology, Simon Frascr Univcrsit,y Date Approved: SIMON FRASER UNIVERSITY LIBRARY Declaration of Partial Copyright Licence The author, whose copyright is declared on the title page of this work, has granted to Simon Fraser University the right to lend this thesis, project or extended essay to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. 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Simon Fraser University Library Burnaby, BC, Canada Revised: Summer 2007 STATEMENT OF ETHICS APPROVAL The author, whose name appears on the title page of this work, has obtained, for the research described in this work, either: (a) Human research ethics approval from the Simon Fraser University Office of Research Ethics, (b) Advance approval of the animal care protocol from the University Animal Care Committee of Simon Fraser University; or has conducted the research (c) as a co-investigator, in a research project approved in advance, (d) as a member of a course approved in advance for minimal risk human research, by the Office of Research Ethics. A copy of the approval letter has been filed at the Theses Office of the University Library at the time of submission of this thesis or project. The original application for approval and letter of approval are filed with the relevant offices. Inquiries may be directed to those authorities. Bennett Library Simon Fraser University Burnaby, BC, Canada Last rewslan Summer 2007 Abstract Virtual Reality Environments are becoming increasingly common in the design of auto- mobiles and airplanes for their potential to reduce labourious and time intensive design processes. Unfortunately, variations in users' abilities to correctly perceive depth using vir- tual reality displays are a substantial obstacle to their use in industry. To examine this problem, a psychophysical experiment was conducted using a staircase method to observe how the difference threshold in a distance discrimination task varied in comparisons of real and virtual stimuli. A questionnaire was also used to explore whether the subject's background and previous training, or their ability to tolerate ambiguity could account for individual differences in performance. Results showed significant individual differences, and high variability but no effect was found for the subjects' distance thresholds, although some of the variation in subject response time appears to be related to distance, gender and the cognitive factor of tolerance of ambiguity. Keywords: Depth Perception; Distance Perception; Virtual Reality; Individual Differ- ences; Cognition; Human-Computer Interaction; Psychophysics Subject Terms: Depth Perception; Individual Differences; Cognition; Virtual Reality; Human-Computer Interaction; Psychophysics I tell you the most vivid experience of Virtual Reality is the experience of leaving it. Because after having been in the reality that is man-made, with all the limitations and relative lack of mystery inherent in that, to behold nature is directly beholding Aphrodite; it's directly beholding a beauty that's intense in a way that just could never have been perceived before we had something to compare physical reality to. And that's one of the biggest gifts that Virtual Reality gives us, a renewed appreciation of physical reality. -Jaron Lanier interviewd by Adam Heilbrun for Whole Earth Review in 1988. Interview available at http://www.jaronlanier.com/vrint.html Acknowledgments I would like to thank my Senior Supervisor, Dr. Brian Fisher, for his ongoing support throughout this project, from conference trips, funding and encouragement. I would also like to thank my committee members, Dr. John Dill for his sage advice and support, and Steve DiPaola for standing by me since the very beginning, and for giving me a chance to work with virtual belugas. Thanks also to my external, Dr. Vince Di Lollo, for agreeing to provide his insight on psychophysics at my defense. I am grateful to General Motors Research, and in particular Randall Smith, for providing an interesting problem to work on, for providing use of their software VisualEyes and for allowing me to visit their Detroit Research Centre. Thank you to UBC's Dr. Kellogg Booth and Ron Fussell for allowing me to borrow the equipment for this study. I am eternally grateful to Gordon Pritchard for his endless technical help throughout the last three years, this project would never have come together without his help. Thanks also to Tom Calvert for allowing me to use the Shared Virtual Environment Lab. A huge debt of gratitude to all my family and friends who have been understanding and forgiving of my lack of time over the last few years. Finally, I am grateful to Reynald for motivating me to start this project, for making it fun, and for making sure I finished it. Contents .. Approval 11 ... Abstract 111 Quotat ion iv Acknowledgments v Contents vi List of Tables ix List of Figures x 1 Introduction 1 1.1 Research Area. 1 1.2 Research Questions . 4 1.3 Thesis Organization . 5 2 Literature Review 7 2.1 Depth Perception . , . 7 2.2 Depth Cues . 9 2.2.1 Binocular Depth Cues . 9 2.2.2 Oculomotor Depth Cues: Vergence and Accommodation . 11 2.3 What Is Virtual Reality? . 12 2.4 How Depth Perception is Re-created in Virtual Reality . 15 2.5 Studying Depth Perception in Virtual Reality . 16 2.6 Other Cues Available in Virtual Displays .................... 18 2.6.1 Monocular Depth Cues ..........................18 2.7 Cue Combination ..................................21 2.8 Other Factors Affecting Depth Perception in Virtual Reality .......... 23 2.8.1 Field of View ................................23 2.8.2 Interpupillary Distance .......................... 24 2.9 Research Methods In Depth Perception .....................24 2.9.1 Psychophysics ................................24 2.9.2 Metrics in Virtual Reality Research ................... 26 Background: Previous Work 2 8 3.1 GM's Previous Work ................................28 3.2 Our Previous Work .................................29 3.3 Experiment 1 ....................................29 3.3.1 Materials and Methods .......................... 30 3.3.2 Procedure .................................. 32 3.3.3 Results ...................................32 3.3.4 Discussion ..................................35 3.4 Experiment 2 ....................................35 3.4.1 Materials and Methods ..........................36 3.4.2 Procedure ..................................36 3.4.3 Results ................................... 37 3.4.4 Discussion .................................. 39 3.5 Experiment 3 ....................................40 3.5.1 Materials and Methods ..........................40 3.5.2 Procedure ..................................41 3.5.3 Results ...................................42 3.5.4 Discussion ..................................44 4 Final Experiment 45 4.1 Tolerance of Ambiguity ..............................46 4.2 Adaptation and Previous Experience ......................