A NONLINEAR CHROMATIC MOTION MECHANISM

Previous research has demonstrated two categorically distinct mechanis ms mediating apparent motion of kinematograms composed of eccentricity -confined, randomly placed Gabor micropatterns: a quasi-linear mechani sm operating for high micropattern densities and short time separation s, and a nonlinear mechanism operating at low micropattern densities o r longer time separations, Here we compare the performance of these tw o mechanisms using color (isoluminant) and luminance-defined stimuli. When these stimuli are defined only by their color contrast, the respo nse of the quasi-linear mechanism is severely impaired, while the nonl inear mechanism remains fully operative. This result further strengthe ns the dichotomy between the two kinds of motion perception, and sugge sts that when color vision supports motion perception it does so prima rily, or perhaps entirely, via a nonlinear mechanism. (C) 1998 Elsevie r Science Ltd.