Abstract

Most models of simultaneous and successive hue contrast generally assume similar underlying neural processes, and most experimental results indicate that they produce similar effects. Methodology has often confounded the two effects, however. We show here that for some conditions simultaneous hue contrast yields different results than does successive hue contrast, providing evidence of different neural processes. In four experiments, the red-green null point was used as an indicator of color appearance. In the successive hue contrast condition, a unique blue background was exposed for 10 s of adaptation, followed by a yellow test flash. The null point shifted progressively toward shorter waves as the intensity of the adapting field was increased. Similar results obtained for the usual conditions of simultaneous hue contrast with the center-surround arrangement. However, for brief presentations or with the test stimulus superimposed on the background to control for stray light effects, no such shift occurred in the locus of unique yellow with a unique blue surround. Additional experiments with longer- and shorter-wave backgrounds did produce expected hue shifts, indicating that simultaneous hue contrast effects were nonetheless operative in our conditions. These results suggest that successive hue contrast requires preopponent gain changes, whereas simultaneous hue contrast requires only opponent induction.

© 1985 Optical Society of America