McGurk effect in Finnish syllables, isolated words, and words in sentences: Effects of word meaning and sentence context

The “McGurk effect” is a robust illusion in which subject's perception of an acoustical syllable is modified by the view of the talker's articulation. This effect is not perceived universally but, however, is experienced by the majority of the subjects. For example, if the acoustical syllable /ba/ is presented in synchrony with a face articulating /ga/, English-speaking subjects typically perceive /da/ and less frequently /ga/. We studied the McGurk effect in Finnish syllables, isolated words, and words presented in sentence context in 65 subjects. Audiovisual combinations expected to be perceived either as meaningful words or nonwords were used. Words were also presented in various positions of three-word sentences in which the expected word could match or mismatch with the sentence context. A strong McGurk effect was obtained with each stimulus type. In addition, the strength of the McGurk effect did not appear to be influenced by word meaning or sentence context. These findings support the idea that audiovisual speech integration occurs at phonetic perceptual level before the word meaning is extracted.