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Brett Fajen, Melissa Parade; The accuracy of object motion perception during locomotion. Journal of Vision 2014;14(10):484. doi: https://doi.org/10.1167/14.10.484.
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© ARVO (1962-2015); The Authors (2016-present)
To avoid and intercept moving objects, moving observers must perceive object motion in world coordinates (Fajen, Parade, & Matthis, 2013). This is complicated by the fact that the local optical motion of moving objects is influenced by both observer and object motion, and reflects object motion in observer coordinates. It has been proposed that observers recover object motion in world coordinates by using global optic flow to factor out the influence of self-motion. However, judgments of object motion during simulated self-motion are biased, as if the visual system does not completely compensate for the influence of self-motion. Perceived object motion is less biased when both visual and vestibular self-motion information is available, but is still not completely veridical. The aim of this study was to investigate the accuracy of object motion perception when self-motion is real and actively generated by walking over a ground surface. The experiment was conducted in a virtual environment viewed through a stereoscopic head-mounted display. Subjects observed an object move along a textured ground surface across their path and judged whether the object was approaching or retreating. They performed this task while remaining stationary and viewing optic flow simulating self-motion and while actually walking. We found a bias to perceive objects as approaching when self-motion was simulated. However, judgments were unbiased when self-motion was real, demonstrating that observers are capable of accurately perceiving object motion in world coordinates when self-motion is actively generated by walking over a ground surface. We introduce a new model to account for these and previous findings. The model proposes that non-visual information generated during locomotion is used not to improve the self-motion estimate but rather to allow object motion to be perceived relative to the physical ground surface, so that locomotion and object motion perception are in the same reference frame.
Meeting abstract presented at VSS 2014
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