Cue combination in the motion correspondence problem

Image motion is a primary source of visual information about the world. How ever, before this information can be used the visual system must determine the spatio-temporal displacements of the features in the dynamic retinal im age, which originate from objects moving in space. This is known as the mot ion correspondence problem. We investigated whether cross-cue matching cons traints contribute to the solution of this problem, which would be consiste nt with physiological reports that many directionally selective cells in th e visual cortex also respond to additional visual cues. We measured the max imum displacement limit (D-max) for two-frame apparent motion sequences. D- max increases as the number of elements in such sequences decreases. Howeve r, in our displays the total number of elements was kept constant while the number of a subset of elements, defined by a difference in contrast polari ty binocular disparity or colour, was varied. D-max increased as the number of elements distinguished by a particular cue was decreased. D-max was aff ected by contrast polarity for all observers, but only some observers were influenced by binocular disparity and others by colour information. These r esults demonstrate that the human visual system exploits local, cross-cue m atching constraints in the solution of the motion correspondence problem.