How neural adaptation changes chromaticity coordinates*

Abstract

Color-matching data obtained by Crawford and by Richards imply failures of additivity of color-matching functions. These failures raise serious doubts about the fundamental principles of trichromatic theory. If color matches are made by causing the lights on the two sides of a field to have equal quantum absorptions in the photopigments, and photopigment spectral sensitivities are invariant with adaptation, it is impossible for color-matching functions to be nonadditive. Since the data cannot be faulted, the solution of the dilemma must lie in finding how observers can make matches that violate the assumptions. Known neural interactions in the visual system suggest that the observers were not setting equal quantum absorptions on the two sides of the field. A model of the neural interaction accounts for the departures.