The McGurk effect is a perceptual phenomenon that demonstrates how visual information can influence what we hear. When a person hears a sound while simultaneously watching a video of someone saying a different sound, they may perceive a third sound that blends both inputs. This effect highlights the interaction between auditory and visual stimuli in speech perception. This effect was first identified by psychologists Harry McGurk and John MacDonald in 1976. Their research showed that our brains integrate visual cues, such as lip movements, with auditory signals, leading to a unique auditory experience that may not match the actual sound being produced.