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Jonathan Matthis, Brett Fajen; Visual information about locomotor capabilities and the perception of possibilities for action. Journal of Vision 2010;10(7):1019. doi: 10.1167/10.7.1019.
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© ARVO (1962-2015); The Authors (2016-present)
Navigation through complex, dynamic environments requires people to choose actions that are appropriately calibrated to their locomotor capabilities. For example, when a pedestrian crosses the street, the decision whether to go ahead of an approaching vehicle or wait until it passes must take into account how fast the person can move. When actions are selected before movement is initiated, people can rely on what they know about their locomotor capabilities to select appropriate actions. The aim of this study is to investigate the contribution of visual information picked up on the fly when actions are selected while moving. The experiment was conducted in an immersive virtual environment viewed through a head-mounted display. On each trial, subjects walked 3 m along a tree-lined path, at which point two cylindrical obstacles began to converge toward a location along their future path. Within 1.2 s, subjects had to judge whether they could have safely passed between the obstacles. On a small percentage of trials, the visual gain was increased such that subjects moved through the virtual environment 50% faster than normal. Subjects were more likely to perceive the gap as passable on catch trials with increased visual gain. The increase in “passable” responses is consistent with the use of on-the-fly information, and could be due to global optic flow picked up during the 3 m approach phase or local motion of the converging cylinders. The relative contributions of global flow and local motion were tested in Experiment 2 by increasing the visual gain of the stationary background independently of the moving obstacles. The effect of visual gain was significant, but weaker than in Experiment 1. The findings suggest that when people select actions while moving, they rely on both local and global sources of information that are picked up on the fly.
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