McGurk

The McGurk effect is a perceptual phenomenon in speech perception that occurs when auditory and visual information about speech are incongruent. When the sound and the lip movements do not match, people often perceive a third, fused sound that differs from either input alone. A classic demonstration is hearing the syllable “ba” while seeing lips articulate “ga”; many observers report hearing “da” or another intermediate sound.

Originating in experimental psychology, the effect was described in 1976 by Harry McGurk and John MacDonald in Nature. The phenomenon is named after McGurk and has since become a widely cited example of multisensory integration in the human brain.

Mechanistically, the McGurk effect illustrates how visual information from lipreading can influence auditory speech processing. The perceived result depends on the specific auditory and visual stimuli, as well as individual differences in perception and attention. The effect is robust under many conditions but can be reduced by clearer audio, clearer video, or certain task demands.

Significance and applications of the McGurk effect span multiple fields. It provides evidence for the integration of sensory information in speech perception, informs theories of audiovisual processing, and has implications for clinical approaches in audiology and speech therapy. It also influences the design of multimedia interfaces and technologies that rely on speech synthesis or lip synchronization.

In addition to the phenomenon, McGurk is a surname. People bearing the name have contributed to various disciplines, reflecting the broader use of the term beyond the specific perceptual effect.