The effect of Color-Luminance correlations in surrounding stimuli on color constancy under interocular suppression

Abstract

[Purpose] Changes in illuminant color give rise to correlated changes between luminance and chromaticity across various color surfaces in a scene. Such correlations are considered to subserve color constancy (Goltz & MacLeod, 2002). Simple uniform surroundings are also known to a subserve color constancy (e.g. Valberg & Lange-Malecki, 1990). We investigated the effect of color-luminance correlations in the surround on color constancy using interocular-suppression technique. [Method] We measured shifts in color appearance induced by surrounding color stimuli under conditions with and without perceptual suppression for the surround stimuli. We used a chromatic continuous flash-suppression (CFS: Tsuchiya & Koch, 2005) stimulus to evoke consistent interocular suppression for the surrounding stimuli. In the experiment, a test stimulus was presented at the center of the surrounding stimulus in one eye, and the CFS stimuli were presented to the other eye at a refresh rate of 14 Hz. In conditions without suppression, the test and the surrounding stimuli were presented to both eyes. Either Mondrian- or a uniform-surround was used. The Mondrian-surround stimuli simulated the chromaticity of color chips (OSA uniform color scale) under an illuminant with a broad-band spectrum; the illuminant color was green, white (D65), or red. The uniform surround stimuli had the same mean chromaticity and luminance as the Mondrian stimuli. Observers reported whether the test stimulus appeared reddish or greenish. [Results and Discussion] In the Mondrian condition, color shifts with the CFS were smaller than those without it. In contrast, in the uniform-surround condition, the color shifts were approximately the same between the two suppression conditions. These results may suggest that color shifts induced by color-luminance correlation among surrounding colors at higher stages in visual processing than the stage that integrates binocular information.