Visual Kinematics I. Visual Space Metric in Visual Motion

Visual deformations of moving objects are traditionally attributed to visual mechanisms, such as spatiotemporal summation and visual masking, that transform the distribution of color/brightness in visual space. This paper presents experimental proof that in addition to these distributional transformations, the metric of visual space itself changes in visual motion, Under steady fixation conditions the perceived spatial separation between non-interacting visual images moving with the same physical velocity shrinks along the direction of motion, but not transversely. The ratio of the perceived longitudinal separation-in-motion to the separation-at-rest does not depend on the latter. This ratio decreases with increasing velocity. A simple principle (Mapping Homogeneity) is proposed and experimentally corroborated that conceptually separates geometric transformations in motion from all conceivable transformations of color/brightness distributions in visual space. 63 1992 Academic Press, Inc.