McGurkeffekten

The McGurkeffekten, or the McGurk effect, is a perceptual phenomenon in which conflicting auditory speech input and visual lip movements produce a third, illusory percept. It demonstrates that speech perception is inherently multisensory.

The effect was first described by Harry McGurk and John MacDonald in 1976 in the journal Nature. Their work showed that when people hear one syllable while seeing a different syllable articulated on a video, their perceived sound often combines elements of both inputs into a new percept.

In a classic demonstration, an observer hears the syllable “ba” while watching a video of someone saying “ga.” With the incongruent cues, many listeners report hearing “da” or “tha” instead of either original syllable. The illusion arises from the brain’s attempt to fuse auditory and visual information into a coherent speech percept.

Mechanistically, the effect reflects multisensory integration in the brain, with inputs from the eyes and ears converging in regions such as the superior temporal sulcus to form a unified percept. The strength of the illusion can be modulated by factors such as auditory noise, visual clarity, attention, and task demands.

Significance of the McGurk effect lies in its clear demonstration that vision can shape auditory perception. It has informed theories of speech processing, developmental and clinical research (including autism and hearing impairment), and the design of audiovisual media and assistive listening technologies. Individual susceptibility varies, and cross-linguistic differences can influence the magnitude of the illusion.