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David A. Lessard, Margaret R. Tarampi, Michael N. Geuss, Sarah H. Creem-Regehr, Jeanine K. Stefanucci, William B. Thompson; Overestimating action capabilities for passing through vertical and horizontal gaps under severely degraded vision. Journal of Vision 2011;11(11):904. doi: 10.1167/11.11.904.
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Successful spatial navigation involves the ability to perceive architectural features, such as arches and doorways, as they relate to the possibility of future actions. While navigating spaces, low (degraded) vision individuals may rely on assumptions about architectural features that are consistent with their expectations and previous experience. However, horizontal and vertical gaps (e.g., open stairs, bollards) can vary greatly from one environment to another, potentially posing a navigation hazard. When architectural features are inconsistent, low vision individuals may have to rely more heavily on online visual perception than their expectations. To determine action possibilities, an actor must compare environmental features (e.g., gap width) to relevant body effectors (e.g., body width). In the present studies, participants judged their abilities to pass through horizontal and vertical gaps. They first made these judgments while wearing monocular goggles that reduced acuity and contrast sensitivity and then with monocular goggles allowing otherwise normal vision. Two black poles in front of a white background were presented to participants creating various horizontal gaps. Participants judged yes or no to whether they could pass between the poles without turning their shoulders. Participants also judged yes or no to whether they could pass under a horizontal barrier without needing to duck. The barrier was black and hung in front of a white background. For analysis, judgments were compared to actual body dimensions. Findings indicated that participants made less conservative estimates of action capabilities under low vision conditions than under normal vision conditions. That is, under low vision, participants said they could pass through narrower widths and shorter heights than they reported for normal vision. A study with reverse contrast sign stimuli (white objects in front of black background) is in progress. The inability to correctly perceive environments is a potential safety hazard; this research could inform architecture building guidelines.
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