Color contrast and contextual influences on color appearance.

We used a hue-scaling task to examine changes in color perception resulting from adaptation or induction to color contrast in spatially-varying backgrounds. Observers judged the perceived color of tests after or while viewing backgrounds composed of color differences along selected axes in color space. Both contrast adaptation and contrast induction produced large and selective shifts in perceived hue angle, and interacted in similar ways when combined, suggesting that they had functionally similar influences on perceived hue. Both also consistently biased perceived hue away from the color axis of the background, implying response changes within multiple channels tuned to different directions in color space. Selective hue changes were also observed when the gamut of colors forming the backgrounds were drawn from natural color distributions. This suggests that color perception in different environments may be systematically biased by adaptation to the distributions of colors in those environments. However, we did not find these biases when the same test stimuli were judged after adapting to actual natural scenes.