The edge of an event: Invariants of a moving illusory contour

Abstract

The motion-induced contour is an illusory contour produced between two vertices of an object undergoing the figural transformations of rotation-in-depth (Klymenko & Weisstein, 1980). Although it is not physically present, it is seen at the intersection between the two surfaces of an object where a dihedral edge would normally be located. This illusory contour can be seen despite certain temporal and spatial manipulations of the rotating object. It is perceived during apparent rotation in the intermittent object; and it is also seen in an oblique object where the vertices are not parallel. Of the transformations tested, only rotation-in-depth will produce the motion-induced contour (Klymenko & Weisstein, 1981); however, it is shown here that this is not sufficient. Two complementary factors are necessary. The transformation of rotation-in-depth must specify the structural invariant of a rigid dihedral edge. © 1983 Psychonomic Society, Inc.