Properties of cyclopean motion perception.

This study investigated the ability of human observers to discriminate the direction of laterally-moving cyclopean stimuli, in order to assess some of the properties of stereoscopic mechanisms that mediate the perception of cyclopean motion (motion existing at levels of binocular integration). The stimuli were moving grating patterns created from dynamic random-dot stereograms. Experiment 1 showed that duration thresholds for discrimination decrease with velocity; they are not governed by temporal frequency nor a constant spatial displacement. Experiment 2 revealed that discrimination thresholds increase with disparity magnitude, for both the crossed and uncrossed disparity directions equally. Experiment 3 showed that the rate of temporal variation at and above which direction discrimination fails (cyclopean upper limit of temporal resolution) is 8 Hz. Our results indicate that a mechanism for motion perception exists at binocular-integration levels of the visual system, which supports a model of motion perception that posits the existence of first-order and second-order processes.