Objects in the path of apparent motion

Experiments by several investigators suggest that forms between inducing stimuli for apparent motion may deflect motion from a straight path. In an experiment in which a binocularly viewed object was sometimes positioned between the inducing dots, we discovered that the degree of curvature of the path that is most likely to be reported depends upon the interstimulus interval whether or not the space between inducing dots contains an object. The interstimulus interval at which motion is most frequently reported is longer for curved paths of motion than for linear paths even though the spatial separation of inducing stimuli is held constant. The results suggest that apparent motion in depth is not based upon form.