Abstract
Binocular rivalry (BR) and dichoptic masking (DM) are often-used tools in the study of conscious perception. In BR two incompatible stimuli in the two eyes compete perceptually; in DM a stimulus to one eye becomes invisible when preceded by a stimulus in the other eye, the optimal delay being about 100ms. Spatial aspects of BR, like differences of luminance, contrast, orientation etc. have been extensively studied. Temporal aspects much less so. It is known that BR may occur when images to the two eyes are presented asynchronously without temporal overlap (O'Shea, Crassini, Percept Psychophys; 1984). O'Shea and Crassini found monocular stimulus presentations (T_on) of 10ms, separated by binocular blanks (T_off) up to about 140ms resulted in BR. T_on and T_off were not systematically varied. We chose to systematically investigate how the occurrence of BR depends on T_on and T_off, and found that BR occurred when the sum of T_on and T_off was less than about 150ms, independent of their exact values. In our study, DM was not observed when BR took place, even when one of the two stimuli followed the other at 100ms. When BR broke down (at periods of 2*(T_on+T_off) > about 300ms), DM took effect, and was observed at temporal delays from about 10 to 150ms. BR and DM may rely on a single mechanism with a temporal integration window of about 300ms (i.e. a flicker fusion frequency around 3Hz). During flicker fusion, BR is observed, otherwise DM occurs.