WHAT INDUCES CAPTURE IN MOTION CAPTURE

The phenomenon of ''motion capture'' has been demonstrated by presenti ng, one after the other, two identical Kanizsa squares spatially separ ated and superimposed on a regular matrix of dots. For appropriate tem poral intervals, one illusory square is seen to jump from one location to the other and the dots in it appear to move with it even though th ey are physically stationary. The standard explanation of the effect i s that motion signals from the subjective figure are spontaneously att ributed to the static elements laying on it. We have found, however, t hat if alternative removal of right-angle sectors (required to obtain apparent motion of the illusory square) is not accompanied by alternat ive appearance and disappearance of a few dots, motion capture does no t occur. This suggests that the basic mechanism underlying capture is not the motion of the subjective figure per se, but the spreading of m otion signals arising from those texture elements that alternately go on and off between frames. On the other hand, subjective contours do p lay a role by confining the spreading of motion signals to the texture elements located on the figure.