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Christopher Blair, Jessica Goold, Kyle Killebrew, Gideon Caplovitz; The motion of form features provides a cue to angular velocity. Journal of Vision 2012;12(9):239. doi: https://doi.org/10.1167/12.9.239.
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© ARVO (1962-2015); The Authors (2016-present)
A location along the contour of a rotating object possesses both an angular velocity, which is the same at every location along the contour, and a linear velocity, which is dependent on contour location’s distance from the center of rotation. The question we address here is whether we perceive the angular velocity, linear velocity, or some combination of the two when viewing a rotating object? To address this question we examined how the size of an object influences how fast it is perceived to rotate. If we perceive the angular velocity of a rotating object, then changing its size should not influence how fast it is perceived to rotate. However, as an object becomes smaller, all of the local translational velocities will decrease. Thus, if we perceive the translational velocities of an object, we would expect smaller objects to appear to rotate more slowly than larger ones. A series of psychophysical experiments examined the influence of size on perceived rotational speed for a variety of different object shapes: ellipses, rectangles, rounded rectangles, and stars. Overall, larger shapes were perceived to rotate faster than smaller shapes with the same angular velocity, indicating that observers do not perceive the angular velocity of a rotating object. However, the shape of the object influenced the relationship between size and perceived rotational speed. Specifically, the perceived speed of objects with distinct contour features, such as corners or regions of high curvature, were influenced to a lesser degree by changes in size. Conclusion: the perceived speed of a rotating object is mediated by a combination of two sources of motion information. The first is based on the locally detected component motion and represents linear velocity and the second is based on the motion of distinct form features and represents angular velocity.
Meeting abstract presented at VSS 2012
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