A McCollough Effect Generated at Binocular Site

Following exposures to alternating gratings with unique combination of orientation and colors, an achromatic grating would appear tinted with its perceived color contingent on the grating's orientation. This orientation-contingent color after effect is called the McCollough effect. The lack of interocular transfer of the McCollough effect suggests that the McCollough effect is primarily established in monocular channels. Here we explored the possibility that the McCollough effect can be induced at a binocular site. During adaptation, a red vertical grating and a green horizontal grating are dichoptically presented to the two eyes. In the ‘binocular rivalry’ condition, these two gratings were constantly presented throughout the adaptation duration and subjects experienced the rivalry between the two gratings. In the ‘physical alternation’ condition, the two dichoptic gratings physically alternated during adaptation, perceptually similar to binocular rivalry. Interestingly, following dichoptic adaptation either in the rivalry condition or in the physical alternation condition, a binocularly viewed achromatic test grating appeared colored depending on its orientation: a vertical grating appeared greenish and a horizontal grating pinkish. In other words, we observed a McCollough effect following dichoptic adaptation, which can only be explained by a binocular site of orientation-contingent color adaptation