Abstract
When a figure is segmented from a chromatic background using stereoscopic depth, only weak shifts in color appearance are found (Shevell & Miller, 1996). When, however, a figure is segmented from ground by percepts of transparent layers, shifts in color appearance are large (Wollschlager & Anderson, 2009). Color appearance, therefore, may depend critically on the specific perceptual attributes that segment an object from its chromatic background. This study shows that changes in color appearance due to chromatic adaptation depend on a cortical neural representation at the level of three-dimensional object perception. Shifts in the color appearance of an equilateral-triangle test (0.125 deg in area) were measured using a red/green hue cancellation technique following adaptation to a larger reddish background [L/(L+M) = 0.75, S/(L+M) = 0.2]. The test was perceptually segmented from the background using structure-from-motion so the overall percept was a separate triangular test field on a distinct background. The background was sprinkled with small dots (same chromaticity but slightly higher luminance) that were (i) stationary, (ii) randomly located on each successive frame, or (iii) presented so they were perceived to move coherently over time to create the percept of a 3D sphere. An important feature of the experimental design was that retinal adaptation within 1 deg of the test field was constant in all conditions. When the dot motion created the percept of a 3D sphere, the color shift induced by the background was reduced for three observers, compared to the stationary-dots condition. Randomly relocating dots on each frame also caused some reduction in the influence of the background, but significantly less reduction than when the dots gave the percept of a 3D sphere. In sum, central neural mechanisms of object perception significantly alter the color-appearance changes caused by a given chromatic adapting light.
Meeting abstract presented at VSS 2013