Stimulus similarity modulates sensory dominance effects in cross-modal conflicts

The levels-of-processing framework posits that cross-modal conflicts demonstrate modality-specific dominance patterns, with visual superiority seen at pre-response stages and auditory dominance seen at response stages. However, prior studies have not systematically examined how representational modalities of stimuli during cognitive processing modulate these sensory dominance effects. Given that stimulus similarity influences processing efficiency and conflict magnitude, the present study aimed to examine how stimulus similarity influences sensory dominance effects at both the pre-response and response levels. Experiment 1 (N = 34) adopted a 2-1 mapping paradigm to categorize audiovisual congruency conditions into congruent, pre-response incongruent, and response incongruent conditions to investigate how stimulus similarity influences sensory dominance effects at both the pre-response and response levels. Experiment 2 utilized transcranial electrical stimulation to neuromodulate the left fusiform gyrus (Experiment 2a: N= 26) and left inferior parietal lobule (Experiment 2b: N= 24), causally verifying how stimulus similarity regulates sensory dominance in cross-modal conflicts. In addition to reaction times, the congruency effect index was used to measure the processing level of cross-modal conflicts, and the sensory dominance effect index was used to quantify differences in conflict across different cognitive processing stages. Experiment 1 revealed that visual dominance emerged during pre-response cross-modal conflicts, whereas auditory dominance manifested at the response level. In addition, visual similarity significantly reduced both visual dominance at the pre-response level and auditory dominance at the response level, whereas auditory similarity markedly enhanced visual dominance at the pre-response level. More importantly, Experiment 2 revealed that the effect of visual similarity on the sensory dominance effect in the pre-response stage was related to the left fusiform gyrus. Electrical stimulation of the left fusiform gyrus decreased the visual dominance effect at the pre-response level. The effect of increased auditory similarity at the pre-response level was related to the left inferior parietal lobule, and the visual dominance effect at the pre-response level was increased by anodal electrical stimulation of the left inferior parietal lobule. These findings reveal that stimulus similarity modulates sensory dominance in cross-modal conflicts, with visual and auditory similarity differentially regulating sensory dominance effects at the preresponse level. This study provides novel insights into cross-modal conflict mechanisms across different cognitive processing stages and enhances the understanding of the sensory dominance effect in cross-modal conflicts.