Abstract
When a yellow patch is surrounded either by red or by green dots we perceive chromatic induction on the yellow patch. But both red and green dots surround the yellow patch the chromatic induction is canceled. Here, we report a new phenomenon of chromatic induction. When red and green dots moved at different speeds chromatic induction occurred on the yellow patch that moved at the same speed as either red or green dots whereas chromatic induction disappeared when both red and green dots remained stationary. In the present study we quantitatively investigated this phenomenon. Two yellow squares (1 × 1deg, 20cd/m2), separated by 6-deg distance, were presented one in the top and the other in the bottom half-field of the CRT screen. Red and green dots (0.25deg diameter, 1.1 dot/deg2 for each color) surrounded the yellow squares in both fields. The background was dark (0.1cd/m2). A fixation cross was presented at the center between two squares. The red and the green dots moved at 4.77 and 2.38deg/sec, respectively, in the same direction in one half-field. In the other half-field the red and the green dots moved at the opposite speeds. The yellow squares moved with the higher-speed dots in both half-fields. Most observers perceived chromatic induction (assimilation), stronger than those in the static conditions, in the yellow squares although the magnitude of the effect was different among observers. The results may suggest that chromatic interaction exists within the motion module of the same speed in the visual system.