Summary When viewing a different stimulus with each eye we experience the remarkable phenomenon of binocular rivalry: alternations in consciousness between the stimuli [1, 2]. According to a popular theory first proposed in 1901, neurons encoding the two stimuli engage in reciprocal inhibition [3-8] so that those processing one stimulus inhibit those processing the other, yielding consciousness of one, dominant, stimulus at any moment, the other being suppressed. Also according to the theory, neurons encoding the dominant stimulus adapt, weakening their activity and the inhibition they can exert, while neurons encoding the suppressed stimulus recover from adaptation, until the balance of activity reverses, triggering an alternation in consciousness. Despite its popularity, this theory has one glaring inconsistency with data: during an episode of suppression, visual sensitivity to brief probe stimuli in the dominant eye should decrease over time, and should increase in the suppressed eye, yet sensitivity appears constant [9, 10]. Using more appropriate probe stimuli (Experiment 1) in conjunction with a new method (Experiment 2) we found that sensitivities in dominance and suppression do show the predicted complementary changes. Highlights We devised a new method to probe contrast sensitivity during rivalry episodes Sensitivity of the dominant eye declines; sensitivity of the suppressed eye improves Sensitivities are similar just prior to a switch of perceptual dominance This confirms predictions from reciprocal-inhibition theory of binocular rivalry

This paper presents results from psychophysical experiments on human binocular rivalry in central and peripheral vision. Results show that the incidence of periods of exclusive visibility of a given eye's rival target increased with decreasing target size, and for a given sized target exclusive visibility increased with retinal eccentricity. Control measures confirmed that these results were not attributable solely to reduced peripheral acuity, to Troxler's effect, or to spatial frequency. We computed the minimum-sized stimulus that would lead to a criterion level of exclusive visibility of one or the other eye; this we term the spatial zone of binocular rivalry. The change in estimated size of spatial zones of rivalry with eccentricity compares favorably with estimates of human cortical magnification. We propose a model that assumes concentrically organized zones of rivalry. These zones do not function independently, but instead exhibit a high degree of mutual excitatory cooperativity. The model has multiple solutions for the foveal zone size, but the best fits predict a diameter of 5.3 or 7.3 min of visual angle; these values dovetail nicely with our empirical estimates of the foveal zone size.

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These findings have implications for alcohol education programs targeted at sportspeople and sport administration, and may help improve the efficacy and focus of intervention programs.