Thatcher effect

The Thatcher effect, or Thatcher illusion, is a phenomenon in which changes to facial features are difficult to detect when a face is upside-down, even though the same changes are obvious in an upright face. It is named after the then British prime minister Margaret Thatcher, on whose photograph the effect was first demonstrated. The effect was originally created in 1980 by Peter Thompson, professor of psychology at the University of York.