EXPLANATION OF ILLUSORY CONTOURS IN TERMS OF STRENGTH OF PATTERN AND ITS SPREAD EFFECT

The generation of illusory contours is closely related to distinct par ts of a pattern such as dots, line ends, and corner points. On the oth er hand, the remarkable property is that gaze at one point of the cont ours diminishes the illusion and a return of gaze to the whole pattern restores it. Therefore, illusory contours depend on local parts and t he whole pattern formed by the parts, and fitting data on the two aspe cts is necessary to clarify underlying mechanisms. We have obtained su ch data from the experiments performed to elucidate other visual pheno mena. On the basis of the data, the concepts of strength of pattern, s trength of its spread effect, ridgelines of the spread effect, and a h ollow of the spread effect are introduced and then various phenomena o n illusory contours, including the Kanizsa triangle, are explained in terms of these concepts.