James W. Dias & Lawrence D. Rosenblum University of California, Riverside, USA
This illusion demonstrates that our unconscious ability to lipread is influenced by processes considered idiosyncratic to face perception. It combines two well known effects. The McGurk effect shows that our perception of a heard syllable ('ba') is unconsciously influenced by a synchronized lipread syllable ('va') so we report "hearing" what we see ('va'). The Margaret Thatcher effect shows that the context of a (near) upright face enhances our sensitivity to facial distortions (inverted mouth). In the Rotating McThatcher Illusion, the face rotates around an inverted mouth. When the face is near upright, the influence of the lipread syllable is weakened.