The McGurk-effect (McGurk & MacDonald, 1976) is a robust illusion which is broadly studied in the context of audiovisual integration. In the illusion, auditory speech perception is modified by discrepant visual lip-movements when presented synchronously, leading to a third, not physically present percept. There is an ongoing debate as to whether the percept is integrated early in the sensory system or if it is susceptible to cognitive intervention. Here, the McGurk-effect was studied using gender congruency (face/voice stimuli) as the cognitive intervention to address the question of integration. We first investigated changes in prevalence and reaction times due to perceived gender discrepancy during the McGurk-percept. In the second experiment, neural correlates of the gender discrepant McGurk- percept were studied using fMRI.
We did not find differences in reaction times or accuracy between gender congruent or incongruent stimuli. Thus it appears the McGurk-percept itself is unaffected by gender incongruent stimuli on a behavioural level.
in the fMRI experiment, we found the superior temporal gyrus to reveal a significantly increased activity when the McGurk-effect is perceived as compared to non-McGurk trials, but no effect in this area was found for gender congruency. However, a 2x2 whole brain ANOVA revealed a significant interaction in the face identity processing area (fusiform gyrus) as well as inferior parietal gyrus and superior colliculus. We suggest a mechanism, allowing a stable illusory percept in the gender discrepant McGurk-percept to be facilitated. To our knowledge this is the first study to demonstrate on a neural level that gender congruency affects processing of the McGurk-effect.

McGurk-effect; fMRI; semantic congruency; gender; audiovisual integration