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Making Distance Judgements in Real and Virtual Environments: Does Order Make a Difference?
IntroductionVirtual environments are gaining widespread acceptance as a tool for studying human behavior (Loomis et al., 1999; Plumert et al., 2004). But how well does behavior in virtual environments correspond to behavior in the real environment? Although virtual environments are an exciting new medium for investigating difficult-to-study problems, the results of such experiments are of questionable value if virtual environments lack ecological validity. One critical aspect of behavior in both real and virtual environments is distance perception. Several recent studies suggest that people underestimate distance in virtual environments relative to the real environment (Loomis & Knapp, 2003; Thompson et al., in press; Willemsen & Gooch, 2002).
The conclusion that people underestimate distances in virtual environments may be premature, however. To date, studies examining distance perception in virtual environments have all used head mounted display (HMD) systems. In a recent study using a large screen immersive display (LSID) system, Plumert, Kearney, Cremer, and Recker (2005) found that distance estimates did not differ across real and virtual environments when people made estimates in the real environment first. When people made estimates in the virtual environment first, however, estimates were significantly shorter in the virtual than in the real environment. The goal of this study was to further investigate how the order in which people make judgments in real and virtual environments influences their distance estimates.
Experiment 1: Order Effects on Time-to-walk EstimatesQuestions: (1) How well do time-to-walk estimates correspond in real and virtual environments? (2) Does the order in which an environment is experienced affect distance estimations?
Participants: Forty-eight undergraduates participated for course credit. Environments Real environment. The real environment was an open, grassy lawn in front of a university building. Virtual environment. The virtual environment was a scene depicting the real environment. This scene was displayed on three 10-ft wide x 8-ft high screens placed at right angles to each other. Participants stood midway between the two side screens and 8 ft from the front screen. High-resolution, textured graphics were projected onto the screens (1280 x 1024), providing participants with 270 degrees of nonstereoscopic, immersive visual imagery. The viewpoint of the scene was adjusted for each participant’s eye height. Participants viewed the scene binocularly.
Design and Procedure Baseline walking. We first obtained an estimate of each participant’s typical walking speed by timing how long it took each participant to walk between two points in a hallway. Time-to-walk estimates. After the baseline walking task, participants made estimates of how long it would take them to walk to targets in the real (RE) and virtual environment (VE). Participants made two sets of time-to-walk estimates in one of the following conditions: 1) RE first, VE second; 2) VE first, RE second; 3) RE first, RE second; or 4) VE first, VE second. Participants viewed a person (or an image of a person) standing on the lawn in front of them. They started a stopwatch when they imagined starting to walk and stopped the stopwatch when they imagined reaching the person (without looking at the stopwatch). Participants made estimates of 6 randomly ordered distances in both environments (20, 40, 60, 80, 100, & 120 ft).Measures Actual time-to-walk. We estimated the amount of time actually required to walk the six distances for each participant by dividing each actual distance by the participant’s baseline walking speed. Time-to-walk estimates. Each participant had 12 time-to-walk estimates, representing the time elapsed between starting and stopping the stopwatch for each distance in each environment.
Results Q1: How well did estimates correspond in the two environments? Time-to-walk estimates did not differ significantly across the two environments for either the first or the second estimates (see Figures 1a & 1b). Q2: Did the order in which the environments were experienced effect distance estimations?Although time-to-walk estimates made first were smaller (though not significantly so) in the virtual than in the real environment, time-to-walk estimates made second were virtually identical in the real-real and real-virtual conditions. Summary of Experiment 1 Time-to-walk estimates were similar across the real and virtual environments. Second estimates in the real and virtual environments were almost identical when people experienced the real environment first. This suggests that experience with making distance judgments in the real environment first leads to improvements in distance judgments in the virtual environment. In Experiment 2, we investigated whether this improvement depends on making judgments about identical scenes in both environments.
Christine Ziemer & Jodie PlumertDepartment of Psychology
The University of Iowa, [email protected], [email protected]
James Cremer & Joseph KearneyComputer Science Department
The University of [email protected], [email protected]
Real environment Virtual environment
Figure 1b. Mean time-to-walk estimates made second
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Figure 1a. Mean time-to-walk estimates made first. 0
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