Do you see what you are hearing? Cross-modal effects of speech sounds on lipreading

It is well known that visual information derived from mouth movements (i.e., lipreading) can have profound effects on auditory speech identification (e.g. the McGurk-effect). Here we examined the reverse phenomenon, namely whether auditory speech affects lipreading. We report that speech sounds dubbed onto lipread speech affect immediate identification of lipread tokens. This effect likely reflects genuine cross-modal integration of sensory signals and not just a simple response bias because we also observed adaptive shifts in visual identification of the ambiguous lipread tokens after exposure to incongruent audiovisual adapter stimuli. Presumably, listeners had learned to label the lipread stimulus in accordance with the sound, thus demonstrating that the interaction between hearing and lipreading is genuinely bi-directional.