The natural appearance of an inverted image of a human face in which the eyes (with their eyebrows) and mouth are inverted relative to the face, although the image appears grotesquely hideous when the face as a whole is viewed the right way up, so that only the eyes and mouth are inverted (see illustration). The illusion of normality in the inverted image is believed to be due to the differential inversion effect and the associated difficulty of recognizing configurational incongruities in an inverted face. Also called the Maggie illusion or the Thatcher illusion. [So called because the British psychologist Peter G. Thompson (born 1950) who discovered it in 1980 originally used a photograph of the newly installed UK Prime Minister Margaret Thatcher]
Margaret Thatcher illusion. The inverted face looks almost normal, but it becomes grotesquely hideous when turned the right way up.