Thatcher effect

. The two upside-down images both appear superficially correct as faces. When these images are rotated, however, it becomes clear that the face on the right had its eyes and mouth inverted. 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.

. The two upside-down images both appear superficially correct as faces. When these images are rotated, however, it becomes clear that the face on the right had its eyes and mouth inverted. 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.

Further investigations

The Thatcher illusion has also been useful in revealing the psychology of face recognition. Typically, experiments using the Thatcher illusion look at the time required to see the inconsistent features either upright or inverted. Such measures have been used to determine the nature of the processing of holistic facial images. By looking at the intermediate angles between upright and inverted, studies have explored the gradual or sudden appearance of the illusions. Sensitivity to the Thatcher illusion has been found in children, including children with autism. However, people with congenital prosopagnosia have been shown to exhibit an overall much weaker response to the illusion compared to people without such condition. Their response time was shown to be weakly and linearly affected by the grotesque face's orientation. This last observation suggests that the part of the brain responsible for "configural processing" in face recognition is the fusiform face area of the cortex, which is affected in both the congenital and the acquired condition.

References

Open University YouTube Thatcher illusion demonstration BBC article on the Thatcher illusion Windows utility for "thatcherizing" the face in the webcam (open source)

Text derived from https://en.wikipedia.org/w/index.php?oldid=1357084238 under CC BY-SA 4.0; modifications have been made.