Figure 6.

The similar empirical basis of color contrast (A) and constancy (B). (A) Although the spectral returns from the central squares (indicated by the black dots) are identical, they elicit different sensations of color because the stimuli increase the probability that the two returns originate from differently reflective surfaces under different illuminants. (B) When, however, the spectral information in the scene increases the probability that the returns from the targets originate from similarly reflective surfaces under similar illumination, the central squares (indicated by black dots) elicit relatively similar sensations of color. Thus, despite the fact that the spatial average of the return from the discs surrounding the targets is the same in A and B, the color of two targets appears either different (color contrast) or similar (color constancy), according to the empirical significance of the stimuli.