Visual influences on speech perception processes

An experiment is reported, the results of which confirm and extend an earlier observation that visual information for the speaker’s lip movements profoundly modifies the auditorv perception of natural speech by normally hearing subjects. The effect is most pronounced when there is auditory information for a bilabial utterance combined with visual information for a nonlabial utterance. However, the effect is also obtained with the reverse combination, although to a lesser extent. These findings are considered for their relevance to auditory theories of speech perception.