Perceptual deformation induced by visual motion

The perceived position of a moving object can be misleading because the obj ect has advanced while its previous retinal image has been transmitted thro ugh the visual stream, leading to a mismatch between actual location and it s neural representation. It has been suggested that the human visual system compensates for neural processing delays to retrieve instantaneous positio n. However, such a mechanism would require a precise measure of the actual delay in order to provide a reliable position estimate. A novel illusory de formation of moving contours demonstrates that humans misjudge the spatial relationship between parts of coherently moving targets, and therefore do n ot perfectly account for neural delays. The size of this deformation increa ses with growing speed. In some subjects this illusion can be reversed by v arying the luminance of individual dots; a manipulation that affects the ne ural delays. Our experiments agree with other evidence that the capacity of the visual system to compensate for processing delays is limited.