Perceptual proof that inattention abolishes binocular rivalry

Abundant psychophysical evidence indicates that attention can influence the fluctuations in perception that characterize binocular rivalry. Here we ask an even more fundamental question: can binocular rivalry even occur without attention? Recent psychophysical1,2 and EEG3 results imply that rivalry ceases altogether when rival stimuli are unattended. We used a novel paradigm to provide perceptual verification of this important conclusion. This involved overcoming an obvious problem: rivalry perception cannot be reported by an observer whose attention is fully allocated elsewhere. Our observers therefore reported perception immediately before withdrawing attention from rivalry and again, a few seconds later, upon returning attention to rivalry. Because an individual’s percept durations during rivalry tend to fall within a narrow range (i.e. the duration distribution is tightly peaked rather than uniform), a strong statistical association normally exists between perception at one moment and perception seconds later. This same association is expected between two moments straddling a period of inattention if and only if rivalry continued during that period. In a baseline condition we determined the exact association between perception of a rival stimulus at two moments some time apart. In a second condition we observed that this association was abolished when replacing the stimulus with a blank screen during the period separating the two moments. In the third condition the stimulus remained, but attention was withdrawn. Results from this third condition strongly deviated from the association observed in the first condition. Instead, reports exactly matched those obtained in the second condition where the rivalry conditions were physically removed. Thus, disregarding a stimulus that ordinarily produces binocular rivalry is tantamount to removing it from view. Inattention, in other words, abolishes binocular rivalry. 1. Cavanagh & Holcombe, VSS 2006; 2. He et al, VSS 2007; 3. Zhang et al (2011), Neuron 71(2): 362-9 Meeting abstract presented at VSS 2012