McGurk Effectillusion

McGurk effect/illusion, named after the Scottish psychologist Harry McGurk (1936-1998), is a phenomenon in audiovisual speech perception in which synchronous, but conflicting, auditory and visual phonetic information is presented to participants who typically report -under such circumstances - hearing a "blend" or a "combination" of the seen and heard utterances. The original procedure employed in demonstrating this effect had normal-hearing participants repeat the consonant-vowel syllables they heard while watching and listening to the videotaped face of a speaker. The videotape was created such that the seen (visual "face-articulated") and heard (auditory) speech syllables had conflicting consonants, but were nevertheless presented in synchrony. For example, a visual, "face-articulated" stimulus "ga" accompanied by an auditory/heard stimulus "ba" was reported by participants as being heard as a "da" or "tha;" and a visual, "face-articulated" stimulus "ba" accompanied by an auditory/heard stimulus "ga" was reported as being heard as "bga." In another case, when the videotaped face visually articulates "gi" and the auditory stimulus that is presented is "bi," participants typically report hearing "di." Furthermore, the audiovisual integration of the effect occurs even when participants are told explicitly of the dubbing procedure involving visual and auditory stimuli, or when they are asked to attend to only one (i.e., auditory or visual) of the information streams. Since the original report on the McGurk effect - the influence of vision on speech perception - there have been numerous replications of the phenomenon as well as results concerning a number of basic facts about audiovisual integration in the effect, including the following: it is influenced by the vowel context in which the consonants are spoken; vowels themselves may show the effect; the visual information for place of articulation may influence the auditory perception of consonants that differ in voicing; participants may be sensitive to the concordance of the time-varying aspects of speech but they do not require temporal coincidence of that information; the effect is sustained under substantial changes in the visual stimulus; it occurs with the use of both elaborate and schematic synthetic visual stimuli; an integration may occur over auditory and visual signals generated by speakers of different gender -indicating that the two information streams need not appear to emanate from the same source; and images that involve no identifiable facial features (e.g., use of only a few illuminated dots on a darkened face) may also influence heard speech. Moreover, the McGurk effect has been found in participants of different ages, as well as with various native-language backgrounds. Thus, the McGurk effect/illusion appears to be "robust" to the extent that it holds over substantial visual stimulus changes, is maintained regardless of what the participant knows about the stimuli, and is not decreased when the participant has had considerable practice at selectively attending. See also FACE RECOGNITION/FACIAL IDENTITY THEORY; SPEECH THEORIES. REFERENCES

McGurk, H., & MacDonald, J. (1976). Hearing lips and seeing voices. Nature, 264, 746-748.

Massaro, D. W. (1987). Speech perception by ear and eye: A paradigm for psychological inquiry. Hillsdale, NJ: Erlbaum.

Hearing by eye: The psychology of lip-reading. Hillsdale, NJ: Erlbaum.

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