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Brett Fajen, Sean Barton, Scott Steinmetz; The visual control of walking over terrain with multiple raised obstacles. Journal of Vision 2018;18(10):181. doi: https://doi.org/10.1167/18.10.181.
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When humans walk over flat terrain with regions of unsafe footholds (puddles, patches of ice), visual information from two step lengths ahead is sufficient to maintain forward progress and ensure proper foot placement (Matthis & Fajen, 2013, 2014). However, when the terrain varies in elevation, walkers must also ensure that they avoid colliding with obstacles as the feet move from one foothold to another. The aim of the present study was to determine how far ahead along the future path walkers need to see to negotiate terrain with multiple raised obstacles. Subjects (N = 14) walked along a short path while attempting to avoid stepping on or colliding with virtual obstacles. The obstacles were projected onto the floor by a 3D-capable projector and viewed through shutter glasses (Diaz et al., 2015), giving the impression of a textured ground surface upon which rested an array of randomly distributed 3D blocks. There was also a control condition in which the obstacles were 2D (i.e., flat). To assess how changes in visual look-ahead affect walking behavior, obstacles were visible only when they fell within a circular visibility window centered on the subject's head. Visibility window size varied between 1.0 and 4.0 step-lengths, and there was also a control condition is which the entire obstacle array was visible throughout the trial. As visibility window size decreased, subjects walked slower and were more likely to collide with obstacles in both the flat and raised obstacle conditions. However, effects of the visibility window manipulation were observed at larger window sizes in the raised-obstacle condition, suggesting that walkers require visual information from farther ahead when obstacles are elevated. Additional analyses suggest that such information could be used to more precisely control foot placement and elevation and to select routes that avoid more difficult obstacle configurations.
Meeting abstract presented at VSS 2018
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