Visual control of foot placement when walking over complex terrain

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Matthis, Jonathan Samir
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Electronic thesis
Cognitive science
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In Experiment 1, I demonstrated that two step lengths of visual look ahead is sufficient for humans to walk over complex terrain while exploiting the inverted-pendulum-like structure of bipedal gait as efficiently as they do with unrestricted vision. Experiment 2 revealed that the accuracy of stepping onto a target is unaffected when the target becomes invisible at any point during the step to that target, but sharply declined when the target disappears during the preceding step. Taken together, these findings suggest the existence of a critical period for the visual control of the placement of each footstep that occurs during the preceding step. Experiment 3 supported this hypothesis with the finding that brief presentation of target location during this critical period yields better performance than a longer presentation at a different phase of the gait cycle. However, subjects in that experiment showed a small decrease in performance even if the targets were visible during the critical period. Experiment 4 adjusted the design of this experiment and provided additional support for the critical period hypothesis. The results of these studies suggest that humans use a simple N+1 control strategy to locomotion over complex terrain, which allows them to precisely control the placement of each step while efficiently exploiting the physical dynamics of bipedal gait.
This dissertation presents a research project aimed at investigating the visual control of foot placement when walking over complex terrain with a strong focus on the way that the biomechanical structure of bipedal gait shapes the visual control strategies used to guide human locomotion. In four related experiments, subjects were asked to walk across a path of either randomly arranged obstacles or irregularly spaced target footholds projected onto the floor by an LCD projector. The projector system was synchronized with a full body motion capture system, which allowed for precise experimental control over terrain visibility during the experimental tasks. Examining the way that walking performance varied a function of the availability of visual information about upcoming terrain provides insight into the visual control strategies used to guide foot placement during gait. Furthermore, examining these results in light of the biomechanics of bipedal gait elucidates the way that the physical dynamics of human walking shapes the visual control of foot placement in complex terrain.
August 2014
School of Humanities, Arts, and Social Sciences
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Rensselaer Polytechnic Institute, Troy, NY
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