The role of color in the motion system.

We have examined the ability of observers to determine the direction of movement of a variety of colored plaid patterns. When the two plaid components are of unequal spatial frequency or of unequal luminance or chromatic contrast, observers judge the direction of movement incorrectly. These errors are correlated with a misjudgement of the speeds of the two components. Our results provide support for an initial decomposition into oriented components followed by a subsequent component-to-pattern recombination of moving equiluminant and colored plaids. At equal multiples of threshold contrast a moving luminance grating is about 8 times more powerful than a moving equiluminant grating in determining the apparent direction of motion of a plaid. When both are present, luminance and color do not interact linearly. Color and motion must be processed in parallel in at least partially separate pathways.