ABSTRACT
Orientation-specific color aftereffects (McCollough effects) were shown to produce simultaneous color contrast: An aftereffect elicited by one test grating induced a contrast color on an adjacent test grating. Color contrast tended to be maximal when the spatial frequency of the test gratings were similar to each other; the relative orientation of the gratings. however, had little effect. Colored lights similar to the aftereffects induced colors similar to the colors induced by the aftereffects. The colors induced with the colored lights were likewise sensitive to the spatial frequency of gratings placed on the field and were not sensitive to grating orientation. These experiments suggest that color contrast may partly occur at a cortical level. on the assumption that the McCollough effect involves orientation-selective cortical mechanisms.
