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Abstract

Particularly promising studies on visual awareness generally exploit perceptual bistability phenomena, because they can dissociate the visual input from the perceptual output. To successfully study awareness it is crucial to know the extent to which eye movements alter the input. We have investigated the role of saccades in two perceptual rivalry paradigms (slant rivalry and Necker cube) and in two binocular rivalry paradigms (grating and house–face rivalry). We found that for binocular rivalry, rather than for perceptual rivalry, there is a marked positive temporal correlation between saccades and perceptual alternations at about the moment of the alternation. For binocular rivalry, we further investigated whether saccades can cause perceptual alternations, and if so, whether it is either the execution of the saccade, or the resulting retinal image change that causes the alternation. Subjects viewed repetitive line patterns enabling a distinction of saccades that did produce foveal image changes from those that did not. We found that, although a saccade is not essential to initiate percept changes, the foveal image resulting from a (micro)saccade is a deciding factor for percept dominance. We conclude that the foveal image must change to have a saccade cause a change in awareness.