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Russell Pierce, Zheng Bian, George Andersen; The effects of binocular disparity on the detection of curved trajectories are independent of motion direction. Journal of Vision 2010;10(7):376. doi: 10.1167/10.7.376.
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Pierce, Bian & Andersen (VSS 2009) found that binocular information was important for the detection of curved trajectories. In the current study we examined whether this effect was due to the direction of the motion path. On each trial subjects viewed two computer generated displays. In one display, a sphere followed a straight trajectory; in the other, another sphere moved along either a concave or a convex curved trajectory relative to the x-axis. We used a two-alternative forced choice procedure (2AFC) without feedback and participants were instructed to indicate which display simulated a curved trajectory. Thresholds for curved path discrimination from 16 participants were assessed by varying the curvature of the curved trajectories with an adaptive staircase. We manipulated three independent variables, viewing condition (binocular vs. monocular) curve type (concave vs. convex), and direction of the motion direction path (approaching vs. receding). Each of the 8 combinations was run in a separate block, and the order of blocks was counterbalanced across participants with a Partial Latin Square design. We found thresholds were lower in the binocular condition (M = 6.10 * 10−5) than in the monocular condition (M = 8.55 * 10-5). This difference was greater for concave arcs (M difference = 3.70 * 10−5) than for convex arcs (M difference = 1.19 * 10−5). Whereas the effects for receding objects tend to be weaker than for approaching objects, there was no significant difference between conditions related to motion direction. These results were consistent with our previous finding in support of the importance of the binocular disparity in detecting curved trajectories.
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