Motion parallax as a determinant of perceived depth.

Motion parallax is the optical change of the visual field of an observer which results from a change of his viewing position. It is often denned as the set of apparent motions of stationary objects which arise during locomotion. Psychologists assert that it is a cue for perceiving the depth of the objects, but the optical fact of motion parallax must be distinguished from its capacity to induce perceptions. It has not been experimentally demonstrated that motions in the field of view will actually yield corresponding judgments of depth. This is a purely psychological problem. The optics of motion parallax, on the other hand, is a problem for geometry and ecology. Recently, the suggestion has been made that a continuous gradient of motions in the field of view will induce the perception of slant-depth (J. J. Gibson, Olum, • Rosenblatt, 1955) inasmuch as the perception of depth is intimately connected with the perception of surfaces (J. J. Gibson, ⁹50). This statement also needs experimental test. The purpose of the present study is to investigate what kinds of motion in the light entering an eye do in fact consistently arouse certain judgments of depth, and what do not. The experiments must be carried out with artificial motions in a field of view rather than those obtained