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Thatcher effect

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The Thatcher Effect

The Thatcher effect or Thatcher illusion is a phenomenon where it becomes more 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 former Prime Minister Margaret Thatcher on whose photograph the effect was first and most famously demonstrated. The effect was originally created by Psychology Professor Peter Thompson in 1980.[1]

Overview

The effect is illustrated by two originally identical photos,[2] which are inverted. The second picture is obviously 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 cognitive modules 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 the eyes, nose and mouth.

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.

There is plenty of evidence that rhesus monkeys [3][4] as well as chimpanzees (Weldon et al., 2013) exhibit the Thatcher effect, raising the possibility that some brain mechanisms involved in processing faces may have evolved in a common ancestor more than 30 million years ago.

The basic principles of the Thatcher Effect in face perception have also been applied to biological motion. The local inversion of individual dots is hard, and in some cases, nearly impossible to recognize when the entire figure is inverted.[5]

Further investigations

As well as being a striking illusion, the Thatcher illusion has also been useful in revealing the psychology of face recognition. Typically, experiments using the Thatcher illusion looks at the time required to see the inconsistent features either upright or inverted.[6]<ref>Carbon, C. C., & Leder, H. (2005). When feature information comes first! Early processing of inverted faces. Perception, 34(9), 1117-1134.</ref> Such measures have been used to determine the nature of the processing of holistic facial images.[7]

By looking at the intermediate angles between upright and inverted, studies have explored the gradual or sudden appearence of the illusions.Cite error: A <ref> tag is missing the closing </ref> (see the help page).Lewis, M. B. (2001). The lady's not for turning: Rotation of the Thatcher illusion. Perception, 30(6), 769-774.</ref> The observation of the Thatcher illusion has been found in all groups that it has been tested in. Children observe the illusion, [8]as do children with autism[9] and even people with prosopagnosia.[10] Research shows that the illusion is not unique to humans but can be observed in non-human primates.Cite error: A <ref> tag is missing the closing </ref> (see the help page).Dahl, C.D., Logothetis, N.K., Bulthoff, H.H., Wallraven, C., The Thatcher illusion in humans and monkeys, Proceedings of the Royal Society B: Biological Sciences (2010), 277 (1696), doi:10.1098/rspb.2010.0438.</ref>

See also

References

  1. ^ Thompson, P. (1980). Margaret Thatcher: a new illusion. Perception. doi: 10.1068/p090483
  2. ^ "Reading Upside-down Lips". faculty.ucr.edu. Retrieved 11 April 2013.
  3. ^ Adachi Ikuma, Chou Dina P., Hampton Robert R. 'Thatcher Effect in Monkeys Demonstrates Conservation of Face Perception across Primates', Current Biology 2009, 19, 1270–1273
  4. ^ Dahl Christoph D, Logothetis Nikos K, Bülthoff Heinrich H, Wallraven Christian 'The Thatcher illusion in humans and monkeys', Proceedings of the Royal Society B: Biological Sciences, 2010, 277 (1696)
  5. ^ Mirenzi A, Hiris E, 2011, "The Thatcher effect in biological motion" Perception 40(10) 1257 – 1260
  6. ^ Sjoberg, W., & Windes, J. D. (1992). Recognition times for rotated normal and 'Thatcher' faces. Perceptual and Motor Skills, 75(3, Pt 2), 1176-1178.
  7. ^ Lewis, M.B. & Johnston, R.A. (1997). The Thatcher Illusion as a test of configural disruption. Perception, 26, 225-227.
  8. ^ Lewis, M.B. (2003). Thatcher’s children: Development and the Thatcher illusion. Perception, 32, 1415-1421.
  9. ^ 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. Journal of Child Psychology and Psychiatry|J Child Psychol Psychiatry, 45(7), 1246-1257.
  10. ^ Carbon, C. C., Grüter, T., Weber, J. E., & Lueschow, A. (2007). Faces as objects of non-expertise: Processing of Thatcherised faces in congenital prosopagnosia. Perception, 36(11), 1635-1645.


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