McGurk effect: a standalone construct

Harry McGurk and John MacDonald first reported the effect in 1976 in a paper titled Hearing lips and seeing voices, after finding that a video of a face saying one syllable, dubbed with the recorded sound of a different syllable, made listeners hear a third syllable present in neither track. In their demonstration the sound "ba" played over a face mouthing "ga" is commonly heard as "da", showing that what a person sees on the talker's lips reshapes the phoneme, the smallest distinctive unit of speech sound, that they consciously hear. The illusion persists even when the viewer knows the audio has been altered, which is why it became a standard tool for studying how the brain combines seeing and hearing into a single percept, a process called multisensory integration. Kaisa Tiippana's 2014 review What is the McGurk effect? sets out the working definition now used across the field: the effect occurs whenever visible articulation changes the auditory speech percept, whether the reported syllable is a fusion of the two inputs or one closer to what was seen. What makes it a landmark is its reach, a robust and easily replicated audiovisual illusion that has anchored decades of work on speech perception, attention, development, and the neural sites where the senses meet.[1][2]

Unit

A perceptual illusion, observed per audiovisually mismatched speech token as the syllable a listener reports hearing

Recovery means

Not applicable

Measured by

Quantified as the proportion of incongruent audiovisual trials on which the reported syllable matches the visual articulation or a fused response rather than the acoustic input