Abstract
Introduction: Many inferences about the neural mechanisms of binocular rivalry have been made by studying the relationship between stimulus properties and sustained rivalry oscillations (Brascamp et al., 2015; Levelt, 1965). Yet, little is known about the dynamics of rivalry onset, the time leading up to the initiation of perceptual competition during rivalry, which is thought to be independent from ongoing rivalry oscillations (Carter & Cavanagh, 2007). Here, we examined how both eye- and stimulus-level competition govern the dynamics of rivalry onset by quantifying individual ocular dominance magnitude and varying the degrees of monocular stimuli disparity during rivalry. Methods: 9 adults participated in a binocular rivalry experiment which was composed of 78 trials, 8-second trials (6 practice trials). On each trial, disparate Gabor patches were presented to each eye via a head-mounted virtual reality display. Orientation disparity between the two stimuli varied across trials (60, 90, & 120 degrees). Using a keypad, participants continuously reported their percept (right-tilted, left-tilted, or mixed). Eye dominance magnitude was computed as the difference between the number of trials with dominant vs. non-dominant eye breakthroughs. Results: We found that eye dominance was a significant predictor of average rivalry onset latency (β= -0.032, p=0.019), where individuals with greater eye dominance showed shorter latencies to rivalry onset. We also observed that stimulus orientation disparity was a significant predictor of rivalry onset latency (F(2)=18.4, p=0.026), where smaller stimulus disparities predicted longer rivalry onset latencies. Post-hoc tests indicated significant differences between 120- and 90-degrees disparities (p=0.024). However, the 90-degrees condition (M=1.80, SD=1.62) did not differ from the other two. Conclusion: Together, our results demonstrate that competition at both eye- and stimulus-level contribute to the speed of perceptual resolution during rivalry onset. These results add to our mechanistic understanding of the phenomenon of rivalry onset.