The lightness/pitch crossmodal correspondence modulates reported dominance in binocular rivalry

Crossmodal correspondences (CMCs: systematic associations between feature dimensions across sensory modalities) are known to facilitate performance in simple detection and discrimination tasks and can bias reports of ambiguous figures. The present study tested whether a lightness/pitch CMC biases reported dominance in binocular rivalry. Across three experiments, participants viewed dichoptically presented black and white circles accompanied by relatively high- or low-pitched tones. Dominance reports were coded as congruent when they matched the lightness/pitch correspondence (white/high, black/low) and incongruent when they did not (white/low, black/high). In two experiments, participants reported whether the dominant percept was black or white (direct task); in a third, they judged line orientation while lightness was irrelevant (indirect task). Congruency effects were observed only in the direct task, and only at longer timescales: in intermittent presentation, at 5-s and 8-s exposures; and in continuous presentation, for 5-s sound alternations with responses following tone changes by 1.6-3.2 s, peaking at about 2.6 s. No reliable effects were found in the indirect task. Dominance response durations averaged approximately 2.5 s in the direct task but were significantly longer, approximately 3.5 s, in the indirect task. These results suggest that a pre-existing, untrained lightness/pitch correspondence can bias reported rivalry dominance, but only when the relevant feature is attended and during temporal windows aligned with natural rivalry dynamics. Because dominance was measured by report, the findings are best interpreted as effects on reported dominance rather than as definitive evidence for purely perceptual modulation; nevertheless, they are consistent with subtle crossmodal influences during phases of rivalry instability. OPEN PRACTICES STATEMENT: The data for this study are publicly available on the Open Science Framework (OSF) at https://osf.io/u3ycm/overview?view_only=9fc10ddf4d6c4af8a7d70f2e06c2aef6 . The study was not preregistered.