Facial identity and facial speech processing: familiar faces and voices in the McGurk effect

An experiment was conducted to investigate the claims made by Bruce and Young (1986) for the independence of facial identity and facial speech processing. A well-reported phenomenon in audio-visual speech perception--the McGurk effect (McGurk & MacDonald, 1976), in which synchronous but conflicting auditory and visual phonetic information is presented to subjects--was utilized as a dynamic facial speech processing task. An element of facial identity processing was introduced into this task by manipulating the faces used for the creation of the McGurk-effect stimuli such that (1) they were familiar to some subjects and unfamiliar to others, and (2) the faces and voices used were either congruent (from the same person) or incongruent (from different people). A comparison was made between the different subject groups in their susceptibility to the McGurk illusion, and the results show that when the faces and voices are incongruent, subjects who are familiar with the faces are less susceptible to McGurk effects than those who are unfamiliar with the faces. The results suggest that facial identity and facial speech processing are not entirely independent, and these findings are discussed in relation to Bruce and Young's (1986) functional model of face recognition.