- Thatcher effect
The Thatcher effect or Thatcher illusion is a phenomenon where it becomes difficult to detect local feature changes in an upside down
face , despite identical changes being obvious in an upright face. It is named after British formerPrime Minister Margaret Thatcher on whose photograph the effect has been most famously demonstrated. This was originally created by Peter Thompson, who is a professor at theUniversity of York ,England (Thompson, 1980).Overview
The effect is illustrated by two originally identical photos [http://www.faculty.ucr.edu/~rosenblu/VSinvertedspeech.html] , which are inverted. The second picture is obviously (and quite grotesquely) altered so that the eyes and mouth are vertically flipped, though the changes are not immediately obvious until the image is viewed in normal orientation.
This is thought to be due to specific psychological processes involved in
face perception which are tuned especially to upright faces. Faces seem unique despite the fact that they are very similar. It has been hypothesised that we develop specific processes to differentiate between faces that rely as much on the configuration (the structural relationship between individual features on the face) as the details of individual face features, such as theeye s,nose andmouth . When a face is upside down, the configural processing cannot take place, and so minor differences are more difficult to detect.This effect is not present in people who have some forms of
prosopagnosia , a disorder where face processing is impaired, usually acquired after brain injury or illness. This suggests that their specific brain injury may damage the process that analyses facial structures.See also
*
Face perception
*Prosopagnosia External links
* [http://www.faculty.ucr.edu/~rosenblu/VSinvertedspeech.html Thatcher illusion demonstration]
* [http://www.youtube.com/watch?v=jdADSx8JpfI Open University YouTube Thatcher illusion demonstration]References
Original article
* [http://www-users.york.ac.uk/~pt2/thatcher.pdf Thompson, P. (1980). Margaret Thatcher: A new illusion. Perception, 9(4), 483-484.]
Further investigations
Recognition Times
* Sjoberg, W., & Windes, J. D. (1992). Recognition times for rotated normal and 'Thatcher' faces. Perceptual and Motor Skills, 75(3, Pt 2), 1176-1178.
* Stuerzel, F., & Spillmann, L. (2000). Thatcher illusion: dependence on angle of rotation. Perception, 29(8), 937-942.Developmental aspects
* Lewis, M. B. (2003). Thatcher's children: Development and the Thatcher illusion. Perception, 32(12), 1415-1421.
* Rouse, H., Donnelly, N., Hadwin, J. A., & Brown, T. (2004). Do children with autism perceive second-order relational features? The case of the Thatcher illusion. J Child Psychol Psychiatry, 45(7), 1246-1257.EEG
* Carbon, C. C., Schweinberger, S. R., Kaufmann, J. M., & Leder, H. (2005). The Thatcher Illusion seen by the brain: An event-related brain potentials study. Cognitive Brain Research, 24(3), 544-555.
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