The McGurk Effect

          For my class presentation I demonstrated the McGurk effect. If you watched the video in class, you should have heard the speaker say “tha-tha” or “da-da” as you watched the speaker, and “ba-ba” as closed your eyes. This is due to the McGurk effect, an illusion that demonstrates our perception of speech is influenced not only by the auditory sensation of speech, but also visual information about the speaker’s mouth forming the words. This is an example of multi-modal perception: perception formed by inputs from more than one sense modality, such as hearing and sight. The McGurk illusion is created by dubbing “ba-ba” over video of a speaker saying “ga-ga.” The auditory input of “ba-ba” and the visual input of “ga-ga” fuse into a perception of “da-da” as the brain tries to make sense of the conflicting information.

          The McGurk effect is interesting among examples of multi-modal perception because the conflicting information from hearing and sight leads the brain to fuse the sense information into one perception, rather than one sense completely dominating another. For another example of auditory information affecting visual perception, take a look at the motion bounce illusion. This illusion is much less drastic than the McGurk effect, but it shows how audition can influence how we perceive events in visual space.