Color promotes interocular grouping during binocular rivalry

Abstract

During binocular rivalry local image features distributed over space and between the eyes achieve simultaneous dominance at times; the resulting global figure implicates interocular grouping. Anecdotal evidence suggests that color tends to influence the incidence of global dominance, and in this study we have assessed the strength of this influence on interocular grouping. Experiment 1: We used rival targets like those created by Diaz-Caneja (1928): concentric semi-circles and parallel horizontal lines distributed between the eyes. Using both achromatic and colored versions of these targets, we measured the percentage of time a single coherent figure (e.g., a complete bullseye) was perceived (implicating interocular grouping). Color congruence significantly increased the incidence of interocular global dominance. Experiment 2: Knowing that different parts of an occluded object tend to be perceptually grouped, we manipulated both the color and the shape of partially occluded objects that comprised rival targets. Relative to results with achromatic figures, uniform color paired with shape coherence enhanced interocular grouping, while conflict between color and shape coherence reduced interocular grouping. Experiment 3: Prolonged adaptation to different colors paired with different orientations induces an orientation-contingent color aftereffect (the McCollough effect). Observers first alternately adapted to a red diagonal grating tilted clockwise and to a green diagonal grating tilted counterclockwise. Immediately after prolonged adaptation, observers tracked rivalry between rival figures consisting of achromatic diagonal lines that appeared colored owing to the McCollough effect. Illusory color promoted strong interocular grouping relative to preadaptation testing. Conclusion: Both real and illusory colors are potent contributors to interocular grouping during binocular rivalry.