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Brett Fajen, Melissa Parade, Jonathan Matthis; Humans perceive object motion in world coordinates during obstacle avoidance. Journal of Vision 2013;13(9):120. doi: https://doi.org/10.1167/13.9.120.
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© ARVO (1962-2015); The Authors (2016-present)
When an observer moves through an environment containing another moving object, the local optical motion of the object reflects the relative motion between the observer and the object. However, humans can use self-motion information to recover the component of local optic flow due to object motion alone, allowing them to perceive object motion in world coordinates. What role, if any, does this process play in guiding locomotion in the presence of moving objects? Subjects walked through a virtual environment viewed through a head-mounted display and indicated whether they would pass in front of or behind a moving obstacle that moved on a course to cross their future path. If judgments are based on object motion in world coordinates, then manipulations of perceived self-motion should affect judgments because recovering object motion in world coordinates requires factoring out the influence of self-motion. We manipulated perceived self-motion based on non-visual information by adapting subjects to a ~11° leftward shift of their locomotor trajectory. We then compared judgments on a small percentage of randomly interspersed trials without the lateral shift against judgments on trials from another session in which subjects were not adapted to the lateral shift. Although the relative motion between the subject and the obstacle (and hence the obstacle’s local optic flow) was the same in both sets of trials, subjects were less likely to perceive that they could pass in front on trials in which they were adapted to the lateral shift. Because visual information was the same in both sets of trials, the difference between conditions can be attributed to the adaptation effect, which influenced perceived self-motion based on non-visual information. The findings suggest that when observers choose routes around moving obstacles, they rely on a combination of visual and non-visual self-motion information to recover object motion in world coordinates.
Meeting abstract presented at VSS 2013
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