Chromatic Induction and Perspective Distortion

A pattern presented by Robertson (1996), consisting of yellow and blue square waves with red squares superimposed on either the blue or yellow bands give rise to assimilation effects similar as in the White illusion. The red squares on the yellow bands appear more blue, and the red squares on the blue bands appear more yellow. Varying the position and orientation of the pattern in space changes the effect. For example, slanting the pattern or increasing the distance to the pattern in space increases the effect. But rotating the pattern by 90 degrees and slanting it, nearly eliminates the effect. These changes in color appearance can be explained as the result of averaging in receptive field of extended size.Due to perspective distortion, the area of the pattern in space mapping to an image patch changes with the position and orientation of the pattern. A computational simulation, implementing the distortion from 3D space to image space, followed by a color segmentation (k-means clustering) gave the same color distortion and segmentation as perceived. Thus the effect seems to be simple an artifact of sampling which causes averaging or smoothing with some filters.
We propose the hypothesis that chromatic induction, which takes the two forms of chromatic contrast and assimilation, results, because the system samples with large fields and following in the segmentation stage attempts to compensate for the averaging effects in neighboring regions