Conditions under which stereopsis and motion perception are blind

We describe modified random-dot stereograms in which the corresponding elements differ from non-corresponding elements in colour, size, and luminance. Despite these visible differences between the elements, depth perception collapses when the spatially integrated luminous flux is similar for the corresponding and non-corresponding elements. Our results suggest that a low-pass spatial filter precedes the mechanism that recognises disparity. A similar phenomenon is observed for the perception of coherent motion in random-dot kinematograms. Our modified stereograms and kinematograms may find other uses when experimenters wish to study the contribution of colour to visual processes and require a method of eliminating edge artifacts.