Color from motion: separate contributions of chromaticity and luminance

'Color from motion' describes the perception of a spread of subjective color over achromatic regions seen as moving. The effect is produced with a stimulus display consisting of colored dots, randomly placed upon a white field, with dots in the test region differing in both chromaticity and luminance from those in the surround. Evidence is presented suggesting that color from motion may be regulated by mechanisms different from those for contour formation and color contrast. (1) Results based on ratings show that, in the absence of luminance differences between the dots in the test and those in the surround regions, chromaticity differences alone are sufficient to produce color spread from motion. As the equiluminance point is approached, subjective color spread is seen despite a reduction in the strength of the subjective contour. Thus, contour formation is not likely to be a prerequisite for color from motion. (2) Color matches show that the hue and saturation of the subjective color spread are determined largely by the chromaticity and the luminance of the dots in the test region, not by those of the dots in the surround for the values explored. This suggests that color from motion may arise in sites distinct from those responsible for the regulation of color contrast.