Visual Motion Perception

Abstract

Visual motion provides useful information about the surrounding environment, and this information is extracted and used by biological visual systems in a variety of tasks. Sophisticated mechanisms for extracting and utilizing visual motion are found even in simple animals. For example, the frog has efficient “bug detection” mechanisms that respond selectively to small dark objects moving in its visual field. The ordinary housefly can track moving objects and can discover the relative motion between a target and its background when the two are identical in texture and therefore indistinguishable in the absence of relative motion. Visual motion is also used in the guidance of locomotion and the control of body motion. Another remarkable use of visual motion is the interpretation of structure from motion, which is the recovery of three-dimensional shape using motion information alone. This capacity has been demonstrated in the classical studies of H. Wallach and D.N. O’Connell, in which an unfamiliar object was rotated behind a translucent screen and its shadow projection observed from the other side of the screen. The viewers were able to give a correct description of the hidden object’s three-dimensional structure and motion in Space, even when each static view was unrecognizable and contained no three-dimensional information.