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Brett Fajen, Robert Wild, Sean Barton; Walkers prefer to visually sample the upcoming terrain during the critical phase for visual control of foot placement. Journal of Vision 2017;17(10):706. doi: https://doi.org/10.1167/17.10.706.
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© ARVO (1962-2015); The Authors (2016-present)
When humans walk over complex terrain, they do not need to continuously sample the upcoming ground surface. Even a brief glimpse is sufficient for accurate foot placement if the relevant information is sampled precisely when it is needed to initialize the upcoming step. Previously, we showed that the critical phase for the visual control of foot placement on a given target is the last half of the preceding step. The aim of the present study was to examine whether walkers' preferences for when to sample the upcoming terrain are aligned with the predictions of the critical phase hypothesis. Specifically, we tested the prediction that subjects prefer to sample the upcoming terrain during the same portion of the gait cycle at which sampling is most useful for the accurate control of foot placement. Subjects were instructed to walk along a path of irregularly spaced virtual targets (small patches of light projected onto the floor) while their movements were tracked by a motion capture system. The visibility of each target was manipulated such that targets were only visible for a brief period (e.g., ½ step). The key manipulation was the timing of visibility. Targets could appear and disappear when they were as far as 2 ½ to 2 steps ahead or when they were as close as ½ to 0 steps ahead. After each trial, subjects indicated whether targets were visible earlier or later (farther or less far in advance) than they would have preferred. The results indicated that subjects preferred to sample information about the upcoming targets around the same time that sampling allows for accurate foot placement. The findings could inform our understanding of how walkers decide when to sample the upcoming terrain in situations in which they also need to fixate of other regions of the visual environment.
Meeting abstract presented at VSS 2017
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