Perceptual causality in the amodal completion of kinetic structures.

Perceptual causality as an amodal completion of kinetic structures was demonstrated. The experimental situation was as follows: a square appeared on the left, moved from left to right till it touched one side of a stationary rectangle (a perceptual screen), and disappeared; after a while, another square appeared at the other side of the rectangle and moved right. The first square moved faster than the second one. Sometimes, two moving objects were perceived, with an amodal launching effect: the first moving object seemed to collide with the second one behind the screen. When both the screen and the occluding interval were small, despite the discrepancy of velocities, a single moving object was perceived, but the object seemed to abruptly change its speed behind the screen. The perception of an amodal completion of movement raises some theoretical issues: the discrepancy between amodal completion of kinetic structures and that of static ones, the problem of perceptual identity, and figure-ground segregation in dynamic scene. The dilemma of the naive subject will also be discussed.