Effects of brightness, hue, and saturation on perceived depth between adjacent regions in the visual field

The effects of brightness, hue, and saturation on perceived depth between adjacent regions have been examined. The stimulus consisted of two hemifields of different colors, and the subject was asked to state which appeared nearer and to judge the perceived depth between them. When both hemifields were achromatic, the perceived depth was found to increase with increasing brightness difference. Some subjects tended to judge the brighter side nearer, others the darker side nearer. With the achromatic-chromatic combination, there were no differences in perceived depth among three hue conditions, whilst with the chromatic-chromatic combination the perceived depth depended on hue combination. In terms of decreasing frequency of 'nearer' judgments the hue order was red, green, blue. When the two hemifields differed only in saturation, the perceived depth increased with increasing saturation difference, and whether the effects of brightness and saturation on perceived distance from the observer can be attributed to figure-ground differentiation between adjacent regions in the visual field; but this argument does not cover the effect of hue under achromatic background conditions.