Adaptation and color matching.

Crawford's (1965) experiment [Vision Res. 5, 71-78], implies that there is a failure of linearity when maximum saturation color matches are compared to Maxwell matches. This implication was tested by making the same maximum saturation matches with and without the superposition of a monochromatic desaturating light. A nonlinearity in color matching for short wavelengths was measured without the possible computational or pre-receptoral artifacts in Crawford's design. The data presented are consistent with the hypothesis that this nonlinearity is due to post-receptoral interactions and not to a failure of spectral invariance or to the participation in the match of more than three types of photopigments.