Temporal order detection for foveal and peripheral visual stimuli.

A measure of the temporal resolution of the visual system is the detection of temporal order of the onset of adjacent visual stimuli. The threshold is a few milliseconds and its variation with stimulus separation suggests the existence of a limited processing zone. Measurements were obtained of this distance function in the fovea and retinal periphery of two observers. Temporal order detection threshold does not vary greatly with retinal position out to 20 deg eccentricity, nor does the distance function change much in width, except near the fovea. An independent estimate of the zone for this kind of processing was obtained by testing the range within which signals from oppositely-directed stimulus pairs cancel. Thresholds for dichoptic stimuli are much higher than for monocular or binocular ones.