A BELONGINGNESS PRINCIPLE OF MOTION PERCEPTION

Four experiments are reported that investigated the role of the percei ved coplanarity of a moving target with respect to a frame of referenc e in the third dimension on the perceived path of that target. When a target dot and small moving frame appeared coplanar, the dot's perceiv ed trajectory was governed entirely by its changing position relative to the moving frame. However, when the target and a large stationary f rame appeared in a different plane than the small moving frame, the mo tion of the dot was seen independently of the moving frame. The result s support a belongingness principle of motion perception: The displace ment of an object relative to a frame of reference to which it belongs governs its perceived path of motion.