Unlike sustained rivalry, the weaker stimulus may never achieve perceptual dominance during the onset period of rivalry.
It is clear that the onset phase of rivalry is sensitive to factors that vary between individuals and between regions of the visual field within an individual.
They showed that flashed stimuli, which involves only the onset phase of rivalry, showed up to 20 times greater sensitivity to ocular dominance than continuously presented rivaling stimuli.
Previous studies have demonstrated that the initial period of dominance at the onset of binocular rivalry is likely to be determined by different factors than are responsible for dominance biases during sustained rivalry [21], [22], [24], [36].
The implications of the proposed existence of onset rivalry raises questions about intermediate processes like flash suppression [21] or continual flash suppression [22] which occur when one image is presented continually while the other image is intermittently and repetitively flashed on for brief presentations.
For a model of onset rivalry to be consistent with the results shown here, it would, therefore, need to contain explicit representation of physiological differences for each observer.
One peculiar property of onset rivalry is that the percept that shows a strong bias to dominate in one location may rarely, if ever, dominate in another location of the visual field.
Therefore, the brief presentation of onset rivalry is highly relevant in studying how the brain interprets the rapidly changing, and often inconsistent, signals that are continually received from the eyes.
However, given the small slopes of the relation between the two (negative in two cases and significantly smaller than a slope of 1 in all cases p<0.001), we conclude that there is a large degree of independence between the dominance properties of rivalry seen at onset and that seen during sustained viewing.
