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Kathryn Bonnen, Alexander Huk, Lawrence Cormack; The perception of depth vs. frontoparallel motion assessed by continuous target tracking. Journal of Vision 2016;16(12):183. doi: 10.1167/16.12.183.
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© ARVO (1962-2015); The Authors (2016-present)
We used 3D tracking to simultaneously assess the perception of motion in all directions (horizontal, vertical, and depth). Despite the ecological importance of perceiving motion-through-depth, we found that tracking performance for depth motion was poor compared to frontoparallel motion. Moreover, this impairment was greater than predicted from the small relative size of the retinal signals arising from depth motion. Target-tracking relies on a simple intuition: the better one can see an object or its motion, the more accurately one can point to it. In the main experiment, subjects pointed with their finger to track a stereoscopic luminance circle as it moved in a 3-dimensional Brownian random walk. We measured tracking performance by calculating cross-correlograms for each cardinal motion axis. Tracking performance was selectively impaired for depth motion compared to horizontal and vertical (frontoparallel) motion. The retinal projections resulting from depth motion are, due to geometry, much smaller than those arising from frontoparallel motion, given the same environmental motion extent. In a second experiment, observers tracked a stereoscopic luminance circle as it moved in a one-dimensional Brownian random walk either in depth or horizontally. We systematically manipulated the size of the retinal projection of the motion. This allowed us to isolate a component of the impairment that was independent of signal size. Further experiments ruled out motor explanations. In a final experiment, observers tracked a disparity-defined target in a dynamic random element stereogram as it moved in a 3-dimensional Brownian random walk. When frontoparallel tracking required a disparity computation, tracking performance suffered in a manner similar to the isolated component observed in the retinal projection experiment. Despite the crucial importance of egocentric depth motion, its perception is impaired relative to frontoparallel motion beyond what would be expected from viewing geometry. Disparity processing provides a possible explanation for this impairment.
Meeting abstract presented at VSS 2016
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