Suppressed images selectively affect perceptual dominance in binocular rivalry

Abstract

During binocular rivalry, perception alternates between dissimilar images presented dichoptically. It has traditionally been argued, that the percept during the dominance phase of rivalry is equivalent to that during non-rivalrous monocular viewing. Recent evidence [Pearson, J., & Clifford, C. W. (2005). Suppressed patterns alter vision during binocular rivalry. Current Biology, 15, 2142–2148], however, suggests that the suppressed image can affect perception of the dominant one, yet the extent and nature of this interaction remain elusive. Here we seek to understand the mechanism by which suppressed and dominant images interact. In two experiments, using the same observers, we measured the influence of a mask on discrimination performance for small probes. The probe and masks were presented to either the same eye (monocular: both dominant) or to different eyes (dichoptic: probe dominant, mask suppressed). In the first experiment, both probe and masks consisted of sine-wave gratings. The task was to indicate whether the probe was oriented clockwise or counterclockwise from vertical. The second experiment was similar, but instead of orientation we measured the effect of motion masks in a (left-right) motion discrimination task. All motion stimuli consisted of moving pixel noise. Our results show that performance on orientation discrimination and motion discrimination is affected by the nature of, and the difference in feature space (orientation or motion) between masks and probes. Interestingly, the selective interference of the mask was qualitatively similar for the monocular and the dichoptic condition. This means that perception of dominant images is affected by suppressed images as if the images were actually visible, when in fact they were not.