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Optic flow is used to control human walking


How is human locomotion visually controlled? Fifty years ago, it was proposed that we steer to a goal using optic flow, the pattern of motion at the eye that specifies the direction of locomotion. However, we might also simply walk in the perceived direction of a goal. These two hypotheses normally predict the same behavior, but we tested them in an immersive virtual environment by displacing the optic flow from the direction of walking, violating the laws of optics. We found that people walked in the visual direction of a lone target, but increasingly relied on optic flow as it was added to the display. The visual control law for steering toward a goal is a linear combination of these two variables weighted by the magnitude of flow, thereby allowing humans to have robust locomotor control under varying environmental conditions.

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Figure 1: Manipulating optic flow in a virtual environment.
Figure 2: Predictions of the two hypotheses, in a physical world coordinate frame.
Figure 3: The four virtual worlds, and results of experiment 1.
Figure 4: Mean paths and virtual heading errors in experiment 2.
Figure 5: Visual control law for steering to a goal.


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The research was supported by the National Eye Institute (EY10923), National Institute of Mental Health (K02 MH01353) and the National Science Foundation (NSF 9720327). We thank A. Forsberg for his assistance, and T. Freeman for suggesting the second experiment.

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Correspondence to William H. Warren Jr..

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Warren, W., Kay, B., Zosh, W. et al. Optic flow is used to control human walking. Nat Neurosci 4, 213–216 (2001).

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