Adaptation to transients disrupts spatial coherence in binocular rivalry

When the two eyes are presented with incompatible images, the visual system fails to create a single, fused, coherent percept. Instead, it creates an ongoing alternation between each eyes image; a phenomenon dubbed binocular rivalry (BR). Such alternations in awareness are separated by brief, intermediate states during which a spatially mixed (incoherent) pattern of both images is perceived. A recent study proposed that the precedence of mixed percepts positively correlates with the degree of adaptation to conflict between the eyes. However, it neglected the role of visual transients, which covaried with the degree of conflict in the stimulus design. We here study whether the presence of visual transients drive adaptation to interocular conflict and explain incidence rates of spatially incoherent BR. Across three experiments we created several adaptation conditions in which we systematically varied the frequency of transients and the degree of conflict between the eyes. Transients consisted of grating orientation reversals, blanks, and plaids. The results showed that the pattern of variations in the fractions mixed percepts across conditions was best explained by variations in the frequency of visual transients, rather than the degree of conflict between the eyes. We propose that the prolonged presentation of transients to both eyes evokes a chain of events consisting of (1) the exogenous allocation of attention to both images, (2) the increase in perceptual dominance of both rivalling images, (3) the speed up of adaptation of interocular suppression, and eventually (4) the facilitation of mixed perception during BR after adaptation. Author summaryWhen one eye is presented with an image that is distinct from the image presented to the other eye, the eyes start to rival and suppress each others image. Binocular rivalry leads to perceptual alternations between the images of each eye, during which only one of the images is perceived at a time. However, when the eyes exert weak and shallow mutual suppression, observers tend to perceive both images intermixed more often. Here we designed an experiment and a model to investigate how stereoscopic stimuli can be designed to alter the degree of interocular suppression. We find that prolonged and repeated observations of strong visual transients, such as sudden changes in contrast, can facilitate the adaptation to suppression between the eyes, resulting in that observers report more mixed percepts. This novel finding is relevant to virtual- and augmented reality for which it is crucial to design stereoscopic environments in which binocular rivalry is limited.