A Problem-Solving Approach to Illusory Contours

Abstract

In the illustration shown in Figure 6.1, one can see a white diamond on top of black rectangles (or, alternatively, on top of a black cross). While not all illusory contour effects are identical, the best known and most studied is of this kind, devised by Kanizsa (1955a; 1974). This is the kind of effect I will discuss here. There are three aspects of the illusory contour (IC) phenomenon that require explanation: (1) A contour is perceived where none is present in the display or in its retinal representation, (2) the region bounded by the illusory contours appears to differ in lightness (typically whiter) than the background of the remainder of the display of the same physical luminance, and (3) the fragments that constitute the display tend to appear as amodal representations of larger, more complete entities.