Visual motion, binocular correspondence and binocular rivalry

Human observers dichoptically viewed displays consisting of isotropic random dots, with the dots in each eye's view all moving in a given direction or appearing stationary. When the interocular difference in direction of motion was less than 30 deg, a stable, fused percept resulted. Once this interocular difference was exceeded, binocular rivalry ensued. Rivalry was also obtained when dots seen by the two eyes moved in identical directions but at different velocities. Under this condition, the proportion of time that rivalry was experienced increased with the interocular difference in velocity. Moving dots predominated over stationary ones, and when both sets of dots moved there was no clear advantage of one speed of motion over the other. Contrary to some earlier reports, these results show that motion is not immune to binocular rivalry. Evidently the process responsible for establishing binocular correspondence between images received by the two eyes is sensitive to disparities in direction and velocity of motion.