Fixation shifts in a novel 'no-report' binocular rivalry paradigm induce saccade-related perceptual switches

Abstract

No-report paradigms help to avoid report-related confounds in conscious perception studies. A novel no-report binocular rivalry paradigm by Hesse and Tsao (2020) tracks conscious content using eye position as subjects follow fixation points linked to the rivaling stimuli. However, it remains unclear whether perceptual changes arise spontaneously or are induced by external factors such as fixation shifts and saccades. We found an increased probability of perceptual switches time-locked to fixation point shifts, indicating that some switches are externally driven. To disentangle the effects of visual fixation shifts and saccades, we implemented a two-factorial design and found that saccades play a larger role in eliciting perceptual changes. We estimate that 14% of saccades trigger a switch, accounting for 24% of all perceptual transitions. Our findings provide an analysis framework and guidelines for excluding externally driven perceptual switches, enabling a clearer focus on internally generated perceptual dynamics.