Abstract
Stereo depth thresholds are much higher for stimuli modulated chromatically than they are for stimuli modulated in luminance. It has been suggested that there are independent mechanisms that mediate stereo judgments for the two classes of stimuli. We have tested this theory test by measuring stereoscopic disparity thresholds for luminance modulated targets presented alone, and combined with a chromatic component. This sort of mixture experiment is often hard to interpret but in this case the predicted outcome is simple. If there are independent stereo detection systems, threshold offset for the mixture should be equal to or better than that for the pure luminance stimulus. Thresholds were higher for the mixtures. The results clearly disagree with the independent mechanism hypothesis.