A Description of the McGurk Effect

The clips on the previous pages help to illustrate the McGurk effect. In the first clip, the lips are saying “ma;” in the second clip, they are saying “ka;” but the third clip is not so clear. It is an example of the effect. The McGurk effect is an auditory illusion produced by a visual experience. To produce the effect, the talker was recorded saying the syllable “ma”, and videotaped while saying the word “ka.” The spoken utterance was carefully aligned with the video, resulting in the clip you just saw.

The “m” in “ma” is produced with closed lips (bilabially). “Na” and “ka” are both produced with open lips. In the video clip, the talker has open lips. The visual experience of a talker producing an open-lip sound seems to override our auditory experience of a closed-lip “ma” syllable.

Not everyone experiences the McGurk illusion, though the “ma” + “ka” = “na” form is one of the strongest combinations to produce the effect. Another form that will produce the illusion, at least for some people, is “ba” (auditory) + “ga” (visual) = “da.” Again, “ba” is produced with closed lips, while “da” and “ga” are produced with open lips. Of course, the effect has its limits, and you have probably seen those limits in a badly-dubbed movie. At some point, you realize the words coming out of the actors’ or actress’ mouths are not the same words you are hearing. So, the McGurk effect is limited to similar sounds.