Nonlocal interactions in color perception: nonlinear processing of chromatic signals from remote inducers

Abstract

The perceived color of an object depends on the chromaticity of its immediate background. But color appearance is also influenced by remote chromaticities. To quantify these influences, the effects of remote color fields on the appearance of a fixated 2° test field were measured using a forced-choice method. Changes in the appearance of the test field were induced by chromaticity changes of the background and of 2° color fields not adjacent to the test field. The appearance changes induced by the color of the background corresponded to a fraction of between 0.5 and 0.95 of the cone contrast of the background change, depending on the observer. The magnitude of induction by the background color was modulated on average by 7.6% by chromaticity changes in the remote color fields. Chromaticity changes in the remote fields had virtually no inducing effect when they occured without a change in background color. The spatial range of these chromatic interactions extended over at least 10° from the fovea. They were established within the first few hundred milliseconds after the change of background color and depended only weakly on the number of inducing fields. These results may be interpreted as reflecting rapid chromatic interactions that support robustness of color vision under changing viewing conditions.