The interaction of color, orientation and illusory contour processing

Purpose. The present study examined whether the McCollough (1965) orientation-contingent color aftereffect can be elicited by an occluding object that is completed by illusory contours. Method. Six observers were presented Fig. (1) to their right eyes and Fig. (2) to their left eyes. They were asked whether or not they perceived four complete stripes occluding the two large rectangles. They were also instructed to match the color of a square presented at the bottom of the display with several parts of the test stimuli before and after they were exposed to red and black stripes and green and black stripes alternating every 6 sec for a total of 16 min. Results. Three subjects reported perceiving the four stripes (interpolated with illusory contours). These same subjects also perceived the colors complementary to the colors of the stripes of the adapation stimuli on the surface on which the illusory stripes were perceived. The saturation matched by the subjects who did not perceive illusory stripes was close to zero. Conclusions. The results suggest that the orientation-contingent color aftereffect was obtained on the surface containing the illusory contours. If this color aftereffect is generated in V1 as suggested by several studies, processing of color, orientation, and illusory contours might interact quite early in visual information processing. (Figure Presented).