Abstract

The vividness of traditional subjective-figures and its modulated forms in such a way that the luminance of contrast-inducing elements changes gradually from their centers to the outward directions like a stimulus of Craik-O'Brien -Cornsweet type was compared to investigate the effect of local contrast on subjective contour. From this comparison, it was found that the subjective contours are more vivid in the luminance-modulated figures than the traditional ones. This finding suggests that, if a contrast-inducing element changes gradually in its luminance and becomes indistinguishable with the background at their junction, the activation of line detectors of orthogonal components at the end-cut of the contrast-inducing element is inhibited and consequently interpolating facilitation between the line detectors aligned on a line occurs more easily. However, it was also found that such effect reduces in a large scale when the contrast-inducing element has an isoluminant color. Unlike existing theories, this result suggests that color contrast between a contrast-inducing element and the background may inhibit the occurrence of a subjective contour even in the presence of luminance contrast.