Binocular rivalry and visual awareness: the role of attention

When the right eye and the left eye view dissimilar scenes, the observer do es not experience a stable superimposed percept of the images presented to the two eyes, but instead perceives an alternation between the images seen by each eye. A critical question confronting this robust and intriguing phe nomenon of binocular rivalry is how the visual system selects the image to be perceived (dominant). The current main-stream literature emphasizes a bo ttom-up explanation in which the rivalry stimulus with the higher contour s trength has the advantage, and becomes dominant in rivalry. Nevertheless, s ome workers in the past have favored an attention-selection explanation for binocular rivalry. We investigated the role of attention in binocular riva lry by employing novel psychophysical paradigms which capitalized on severa l established phenomena (eg the Cheshire Cat effect, attention cueing, pop- out effect). Our results revealed two major aspects of attention modulation in binocular rivalry. We found that a dominant image is less likely to be suppressed when voluntary attention is directed to it. This suggests the ro le of voluntary attention in retaining the dominant image in visual awarene ss. Second, a rivalry stimulus is more likely to become dominant if accompa nied by a pop-out cue (in the same eye and proximity). Since a pop-out cue attracts involuntary attention to its location/eye, this result suggests th at cue-mediated involuntary attention can promote the ability of a rivalry stimulus to reach visual awareness.