Kinetic subjective contours

Continuous changes in spatially separated figures can evoke perception of subjective contours and figures in physically homogeneous space between them. This occurs when all of the interruptions in the objectively present patterns (inducing elements) can be seen as caused by a unitary figure partly occluding them. Two experiments demonstrated and explored this phenomenon. In both, displays were presented to subjects under three conditions. In one condition, stationary inducing elements were shown as they would be interrupted by a figure rotating in front of them. In another condition, the background and inducing elements rotated, with interruptions occurring as if a stationary figure were in front. In a third condition, observers were shown 10 static views taken from the figure-rotation sequence for each display. Subjects consistently perceived unitary central figures with well-defined forms and clear edges from pattern changes given by figure movement and background movement. As with static subjective figures, kinetic subjective figures appear in front of, partly occluding, the inducing elements. These percepts form rapidly, and they depend upon temporal relations rather than upon information present in momentary views. Subjects occasionally reported subjective edges or a central figure in the stationary displays in Experiment 1, but not at all in Experiment 2, in which guessing tendencies were reduced by more specific instructions. The existence of kinetic subjective contours suggests that the visual system readily utilizes relationships among occlusion events separated in space and time. The minimum conditions for contour perception require neither information all along an edge nor simultaneous specification of the edge at two or more places.