The Existence of Interpolated Illusory Contours Depends on Contrast and Spatial Separation

Abstract

Subjective, or perceptual, or interpolated contours—whatever we call them, the experience of seeing the borders in demonstrations like Kanizsa’s triangle (Kanizsa, 1955) is fascinating and puzzling. Upon close inspection the apparent border may disappear, yet the initial involuntary perception of a completed contour is compelling. Explanations for the perception of such interpolated contours have ranged from cognitive processes (Gregory, 1972; Prazdny, 1983) to spatial filters (Ginsburg, 1975) to simultaneous contrast (Frisby, 1980). We have approached this problem from a somewhat different direction, based on our prior experience in studying visual neurophysiology. We have investigated the dependence of the existence of interpolated contours on the spatial separation of the inducing elements, and upon their contrast, and have found a strong dependence on these parameters.