COLOR CONSTANCY INFLUENCED BY CONTRAST ADAPTATION

VISUAL sensitivity is controlled by at least two distinct types of ada ptation: light adaptation adjusts sensitivity to the mean luminance an d colour in the stimulus(1), and contrast adaptation adjusts sensitivi ty to the variations in luminance and colour(2-5). Light adaptation is thought to be important in maintaining the perceived colour of object s despite changes in illumination ('colour constancy'), compensating f or the mean changes in the light reflected from scenes under different illuminants(6). But for naturalistic colour signals, we show here tha t changes in an illuminant can also alter colour contrasts in images ( how colours are distributed around the mean) enough to alter the state of contrast adaptation. Thus perceived colour under different illumin ants may also be noticeably influenced by contrast adaptation.