Dichoptically Viewed Colour Aftereffects Produced by Monocular Adaptation

Colour aftereffects were observed in dichoptically viewed achromatic striped patterns after a 25 s period of monocular adaptation to an homogeneous coloured field of red, green, or blue. Three test conditions of dichoptic viewing were used. In condition 1, black line patterns were viewed dichoptically on fused white backgrounds. Stimuli used in condition 2 were similar except that they were white line patterns on black backgrounds. Last, condition 3 was realised with the same stimulus patterns utilised in condition 1, except that the mode of dichoptic viewing produced a juxtaposition rather than a fusion of the two white backgrounds containing the line patterns. Some colour aftereffect was obtained for each colour-adaptation condition and in each test condition. It consisted in a negative colour aftereffect (NCA) in the adapted eye (the colour seen was roughly the complementary of the adaptation colour) and/or a positive colour aftereffect (PCA) in the unadapted eye (the colour seen tended rather to be similar in hue to the adaptation colour). In fact, the following four kinds of responses were obtained: (i) two colour aftereffects, one seen by each eye, ie a NCA involving the adapted eye and a PCA involving the unadapted eye; (ii) a NCA involving the adapted eye only; (iii) a PCA involving the unadapted eye only; (iv) no colour aftereffect at all. Results obtained in different test conditions permitted us to assert that both kinds of colour aftereffect could be produced with white patterns on dark backgrounds as well as with black patterns on white backgrounds and did not require binocular fusion of the white backgrounds. Hypothetical physiological explanations of these aftereffects are available.