Ghazaleh Mahzouni¹, Nicolas Davidenko; ¹University of California, Santa Cruz

The McGurk effect is a multisensory illusion where hearing one sound (/ba/) while seeing incongruent lip movements (/ga/) can produce a new percept (/da/ or /tha/). Previous work has linked individual differences in McGurk susceptibility to gaze patterns (e.g., fewer mouth-directed fixations; Gurler et al., 2015), sensory weighting (Stacey et al., 2021), and individual differences in clinical traits such as autism (Zhang et al., 2019). In Study 1, we investigated whether people with misophonia (characterized as a strong aversion to orofacial sounds like chewing and slurping; Swedo et al., 2021) differ in their susceptibility to the McGurk illusion and to a new audio-visual conflict illusion based on the Sound-Swapped Video database, where trigger sounds (e.g. mouth swishing water) are paired with plausible alternative videos (e.g. shaking a water bottle; Samermit et al., 2022; Mahzouni et al., 2024). We recruited 29 participants with misophonia and 49 controls based on the Duke Misophonia Questionnaire. Participants completed a McGurk task followed by a sound identification task using congruent (e.g., /swishing/, /swishing/) and incongruent (sound-swapped; /swishing/, /shaking bottle/) audiovisual stimuli. We found that misophonic participants were less susceptible than controls to visual influences in the McGurk task but not in the sound identification task. Further, there was no relationship between performance in the two tasks. In Study 2, we recruited 30 new participants and monitored their eye movements as they completed a McGurk task. We replicated our behavioral findings, but found no difference in the proportion of mouth-directed fixations between misophonia and control participants and no relationship between mouth-directed fixations and McGurk susceptibility. Together, our results suggest that lower susceptibility to the McGurk illusion in misophonia is not driven by differences in mouth-directed fixations but perhaps by differences in auditory vs. visual weighting in speech stimuli.