The contribution of color to global motion processing.

This study investigates the contribution of color vision to global motion. We present evidence demonstrating that performance on a global motion task attains similar levels for both types of chromatic (L/M-cone opponent and S-cone opponent) and luminance stimuli at suprathreshold contrasts. We show, however, that the motion thresholds for isoluminant chromatic stimuli are luminance based, on the grounds that they are masked by luminance noise but robust to chromatic noise. Detection thresholds, on the other hand, are chromatic in origin (masked by chromatic but not luminance noise), indicating that there is no luminance artifact in the stimulus. We suggest that for color vision at isoluminance the global motion task is based on the integration of many local, luminance-based signals.