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Aaron Fath, Brett Fajen; Static and Dynamic Information about the Size and Passability of Apertures. Journal of Vision 2010;10(7):1025. doi: 10.1167/10.7.1025.
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Narrow openings between obstacles are among the most commonly encountered potential impediments to forward locomotion. The size of such apertures can be perceived in intrinsic units based on static, eye-height scaled information (Warren & Whang, 1987), allowing one to decide whether to attempt to pass through or select an alternative route. The aim of this study is to investigate the contribution of two sources of dynamic information about aperture size that are also available during approach to an aperture, one of which specifies aperture size in units of stride length (Lee, 1980), and the other that specifies the future passing distance of the inside edges of the aperture (Peper et al., 1994). Experiments were conducted in a 7 m x 9 m virtual environment that was viewed through a head-mounted display (FOV: 44° H x 35° V). In Experiment 1, subjects judged whether they could fit through an aperture between a pair of vertical posts resting on a ground plane, an aperture between a pair of vertical posts without a ground plane, and an aperture in an untextured frontal wall without a ground plane. Because the ground plane was absent and the posts and wall spanned the entire vertical FOV in the last two conditions, static, eyeheight-scaled information was not available and subjects had to rely on dynamic information. Analyses focused on the accuracy of passability judgments that were made while stationary versus immediately after walking 3 m toward the aperture. In Experiment 2, subjects were instructed to walk toward the aperture and rotate their shoulders if necessary to safely pass through without colliding. Analyses focused on the timing and magnitude of shoulder rotation under the same three viewing conditions used in Experiment 1.
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