Abstract
Research on visual awareness often employs rivalrous stimuli. It remains unknown why rivalry manifests itself in various distinct ways. A widely supported view is that monocular rivalry, binocular rivalry and stimulus rivalry depend on different rivalry mechanisms, because their instigation depends on different temporal and spatial stimulus characteristics, and their evoked perceptual alternation dynamics are distinctly different.
We used orthogonal sine-wave gratings that were repetitively presented with a certain on- and off-period duration. To produce stimulus rivalry or monocular rivalry the patterns were swapped between or within the eyes, respectively, at each successive cycle. First we show that with these stimulus and monocular rivalry stimuli we could induce rivalry for spatial frequencies and contrast values that are generally thought to preclude rivalry.
We then looked into the perceptual dynamics. Generally, binocular rivalry is found to have rapid alternations of percepts, and short transition periods between two dominant percepts, whereas monocular rivalry has slow alternations and long transitions periods. We observed the same dynamics when presenting the stimuli without a blank: binocular rivalry showed average percept durations around 2 seconds, and monocular rivalry around 8 seconds. However, with relatively long blank periods and relatively short repetition cycles, the perceptual dynamics for stimulus rivalry and monocular rivalry are identical to those of binocular rivalry: transition periods between successive dominance periods are short, and perceptual alternations rapid (around 0.5/s). Our data—on both the dependence on spatial parameters, and on the perceptual dynamics of rivalry—strongly suggest a single mechanism underlying multiple types of grating rivalry.