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Russell Pierce, Zheng Bian, George Andersen; The effect of binocular disparity on the detection of curved trajectories. Journal of Vision 2009;9(8):265. doi: https://doi.org/10.1167/9.8.265.
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The current study examined the roles of binocular disparity and object motion on the detection of curved trajectories. Subjects were shown computer generated displays of a lit sphere (diameter of 3.8cm) that traveled through the display at eye height from a starting position (22.3cm to the left of and 138.5cm away from the observer) to an ending position (15.3cm to the right of and 100.8cm away from the observer). On each trial subjects were shown two displays. In one display the sphere followed a straight trajectory; in the other it moved in either a concave or convex arc relative to the x-axis. A two-alternative forced choice procedure was used without feedback and subjects were asked to indicate which display simulated a curved trajectory. A BEST PEST procedure was used to adjust the radius of the circle that defined the arc to determine the point of subjective equality (PSE). Two independent variables were manipulated: viewing condition (binocular vs. monocular) and arc direction (concave vs. convex). The four conditions were run in separate blocks and order was counterbalanced across participants with a Partial Latin Square design. We found that subjects' PSE was lower for binocular (mean radius of curvature of 98.0cm) as compared to the monocular condition (mean radius of curvature of 72.4cm). Additionally concave trajectories were easier to detect than convex trajectories. These results support the notion that binocular information is important for the detection of curved trajectories. The results also indicate the importance of the sign of curvature, suggesting that the rate of change of disparity is important in detecting curved trajectories.
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