Question 1

What is the McGurk effect?

Accepted Answer

The McGurk effect is a perceptual illusion in which watching a person's lip movements changes the speech sound you hear. When a mouth saying "ga" is paired with an audio "ba," most people hear a third syllable, "da," that exists on neither channel.

Question 2

Why do you hear a different sound when you watch someone's lips?

Accepted Answer

Your brain always fuses sight and sound when processing speech. When the visual and auditory signals conflict, it manufactures a compromise sound whose place of articulation satisfies both senses, which is why a visible "ga" and an audible "ba" produce the heard "da."

Question 3

Can you stop the McGurk effect once you know how it works?

Accepted Answer

No. The illusion survives full knowledge of how it operates. Even after understanding the mechanism and watching the demonstration repeatedly, your brain still delivers the fused syllable automatically, because the sensory fusion happens below conscious control.

illusions

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The Syllable That Was Never Spoken