Do identical percepts from multiple ambiguous neural representations depend on the suppressed competing representations?

Perceptual resolution for multiple identical dichoptic stimuli will result at any given moment in some neural representations being dominant, so perceived by the observer, and others being suppressed. Often, a suppressed representation will become dominant (and the prior dominant representation will become suppressed) simultaneously for all the dichoptic stimuli so the observer perceives all stimuli as identical (Kovács et al., 1996), a phenomenon referred to as ‘grouping’. It is unclear, however, if the dominant and the suppressed neural representations must both be identical for every stimulus in view for grouping to occur; experiments here tested whether grouping is dependent on both representations. METHODS Stimuli were two dichoptic chromatic discs presented using interocular-switch rivalry to isolate a binocular level of neural competition (Slezak & Shevell, 2018). The possible percepts at each retinotopic location differed among conditions, though a grouped percept of both discs appearing the same color always was possible. A control condition had matched competing chromatic representations at both locations (e.g., both discs dichoptic red/green); a ‘mismatch condition’ had one matching and one different competing chromatic representation in the two locations (e.g., one disc dichoptic red/green and one dichoptic red/purple), so that only one possible percept could be grouped (e.g., red/red). RESULTS/CONCLUSIONS All five observers showed significant grouping when both dichoptic discs had identical possible percepts (control condition) while only one observer showed significant grouping when the discs had different alternative percepts and thus different neural competition at each location (mismatch condition). Further, four of five observers perceived grouped colors significantly more often when there was identical competition in both locations (control condition) than when it was not identical (mismatch condition). This indicates that grouping occurred significantly more often when the dominant and the suppressed representations were each identical, supporting the theory that fully identical competing neural representations drive grouping.