When Hearing Lips and Seeing Voices Becomes Perceiving Speech: Auditory-Visual Integration in Lexical Access.

In the McGurk Effect, a visual stimulus can affect the perception of an auditory signal, suggesting integration of the auditory and visual streams. However, it is unclear when in speech processing this auditory-visual integration occurs. The present study used a semantic priming paradigm to investigate whether integration occurs before, during, or after access of the lexical-semantic network. Semantic associates of the un-integrated auditory signal were activated when the auditory stream was a word, while semantic associates of the integrated McGurk percept (a real word) were activated when the auditory signal was a nonword. These results suggest that the temporal relationship between lexical access and integration depends on the lexicality of the auditory stream.