  The neural networks of the human visual brain derive representations of
three-dimensional structure from specific two-dimensional image cues. Neural
models backed by psychophysical data predict how local differences in either
luminance contrast or physical size of local boundaries in 2D images may
determine the perception of 3D properties. Predictions relative to the role of
color in this process do not follow from any of the current models. To further
clarify the potential contribution of color to perceptual organization, image
configurations with multiple surface representations where the relative
physical size of local boundaries between contrast regions was held constant
were submitted to perceptual judgments of relative size and relative depth. The
only potential cues available in the images were generated by the specific
local combinations of color and luminance contrast. It is shown that response
probabilities for subjective depth and subjective size are systematically and
consistently determined by local surface colors and their immediate
backgrounds. There is a statistically significant correlation between
subjective depth and subjective size, and a color specific effect on both
dependent variables. This effect depends on the polarity of the immediate
surround of the reference surface rather than on local center-surround contrast
intensity. It is suggested that the underlying neural mechanisms selectively
exploit specific color and background cues to enable intrinsically coherent
perceptual organization of ambiguous image input.
