Binocular stereopsis without spatial disparity

Binocular stereopsis has traditionally been studied mainly under static viewing conditions. There has consequently been the tendency to view binocular stereopsis only in terms of the pickup of purely spatial (time-frozen) disparity. However, whenever there is movement of objects or the 0, the structure of the light entering each eye undergoes continuous change, and so a different type of disparity—kinetic disparity—is made potentially available to the binocular system. That kinetic disparity can, in fact, be picked up is shown by the present experiment, in which there was no spatial disparity information available about the three-dimensional motion path of an object; only kinetic disparity information was available. This suggests that a clear distinction should be made between binocular-static and binocular-kinetic space perception.