Subjective Contour Strength and Perceptual Superimposition: Transparency as a Special Case

Abstract

According to Kanizsa (1979), “The modification of brightness in the typical subjective contour stimuli is not the cause, but a consequence of the particular spatial configuration that the perceptual field is forced to assume” (p. 204). Recent data from Cavanagh (1986) expresses an alternative viewpoint. Although Cavanagh is not particularly arguing against Kanizsa’s point of view, his finding that isoluminant stimuli do not evoke subjective contours can be used as a valid counter argument against the view of brightness change as a consequence rather than a cause. The lack of strong subjective contours with isoluminant stimuli has been reported several times (Brigner & Gallagher, 1974; Brussell, Stober, & Bodinger, 1977; Frisby & Clatworthy, 1975; Gregory, 1977).