Multiplicative nonlinearity in the perception of apparent motion.

Evidence is reported indicating that the perception of apparent motion is better predicted by the multiplicative combination of luminance changes at two element locations than by the sum or squared-sum of the luminance changes, or by the motion energy in the stimulus. Because the results were obtained with a stimulus for which motion was specified by simultaneous luminance changes, they support a Reichardt-style motion detector model, but without the asymmetrical delay specified by current versions. Motion direction in the modified model relies on asymmetrical stimulus information rather than asymmetrical delay. That is, one subunit of the detector responds to changes in luminance toward the background luminance (the start of the motion path), and the other to changes in luminance away from the background luminance (the end of the motion path).