The McGurk effect describes the perceptual illusion that occurs when the visual perception of a sound (seeing lips move) is paired with the auditory information of a different sound which produces a perception of a different third sound. Hearing and visual cues work together when we are perceiving speech. When a person hears a different sound than what the visual information suggests it can cause a perceptual illusion. People who frequently watch dubbed foreign language films are immune to this effect because they are used to seeing lips move that are paired with different sounds. This phenomenon was first introduced by McGurk and McDonald (1976) when researching visual information for speech comprehension.