Academic journal article Attention, Perception and Psychophysics

Revisiting the Effect of Quality of Graphics on Distance Judgments in Virtual Environments: A Comparison of Verbal Reports and Blind Walking

Academic journal article Attention, Perception and Psychophysics

Revisiting the Effect of Quality of Graphics on Distance Judgments in Virtual Environments: A Comparison of Verbal Reports and Blind Walking

Article excerpt

In immersive virtual environments, judgments of perceived egocentric distance are significantly underestimated, as compared with accurate performance in the real world. Two experiments assessed the influence of graphics quality on two distinct estimates of distance, a visually directed walking task and verbal reports. Experiment 1 demonstrated a similar underestimation of distances walked to previously viewed targets in both low- and high-quality virtual classrooms. In Experiment 2, participants' verbal judgments underestimated target distances in both graphics quality environments but were more accurate in the high-quality environment, consistent with the subjective impression that high-quality environments seem larger. Contrary to previous results, we suggest that quality of graphics does influence judgments of distance, but only for verbal reports. This behavioral dissociation has implications beyond the context of virtual environments and may reflect a differential use of cues and context for verbal reports and visually directed walking.

In head-mounted-display-(HMD-)based immersive virtual environments (VEs), observers underestimate absolute egocentric distance. They walk, throw, and verbally respond as if distances are closer than they are intended to be (Durgin, Fox, Lewis, & Walley, 2002; Loomis & Knapp, 2003; Mohler, Creem-Regehr, & Thompson, 2006; Richardson & Waller, 2007; Sahm, Creem-Regehr, Thompson, & Willemsen, 2005; Thompson et al., 2004; Willemsen, Gooch, Thompson, & Creem-Regehr, 2008). Now, numerous research studies have explored many of the possible reasons for this systematic effect on distance judgments. One intuitive factor, and the manipulation in the present study, is the nature of the computer graphics. The cartoon-like nature of some graphics used in VEs may influence perceptual fidelity by affecting cues for absolute distance, such as familiar size. Subjective experience supports this claim, since more realistic, higher-graphicsquality- rendered spaces seem larger than equivalently sized spaces rendered with less realistic textures and objects. In contrast to this anecdotal experience, Thompson et al. (2004) found no significant difference in egocentric distance judgments between three distinctly different qualities of graphics presented in a VE. Thompson et al.'s (2004) study focused on one type of distance estimation, triangulation by walking, in which observers viewed a target and walked indirectly toward that target. The present study builds on this work by asking a question more targeted to perceptual mechanisms, examining whether the effects of quality of graphics are generalizable across two different types of response measures. Given the striking contrast between one's "sense" of the size of the space and the objective measure of visually directed walking, we questioned whether quality of graphics might affect verbal reports of distance more than it does a visually directed walking measure. We conducted two experiments to assess the potential dissociation between visually directed walking and verbal reports of distance in HMD-based VEs as a function of the quality of graphics. Assessing the generalizability of the effects of quality of graphics on distance judgments has both theoretical implications for the unitary nature of perception and action and applied significance for the utility of HMD-based VEs in domains such as training, education, and rehabilitation.

Distance Perception in Virtual Environments

Simulations used for training, education, and prototype/ model walkthroughs should reliably convey real-world spatial characteristics and constraints in order for knowledge and skills acquired in VEs to transfer seamlessly to the real world. For example, a number of studies have suggested that changes in perceptual-motor calibration induced in VEs can significantly influence subsequent actions performed in the real world (Fox & Durgin, 2003; Mohler et al. …

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