Abstract
We used the McCollough color/orientation aftereffect to investigate the cortical representation of color. Previous researchers have measured the apparent color shift visible on neutral gray test patterns, whereas here we use colored tests. Subjects adapted to pairs of perpendicular gratings of different colors, and aftereffect strength was assessed by nulling the resulting aftereffect on test gratings. We organized test and adapting gratings on a color line running from green (−) to yellow (0), to red (+) in cone excitation space, summarized here as (adapting colors),test color. In condition (−4, +4),0 subjects adapted to medium saturated green & red pairs of perpendicular gratings and then aftereffect strength was measured on neutral yellow gratings. This gave a larger effect than in condition (0,8),0 with yellow & saturated red adapting gratings. We also measured color aftereffects on red test gratings. Here we found the reverse: the green & red adapter (−4, +4), 4 produced the same or less of an effect as the yellow & red one (0, 8),4. This shows that the effectiveness of adapting colors depends on the test colors, and is suggestive of a non-linear distortion of color space that is the largest in the region in between the adapting colors.