Thatcher illusion

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The Thatcher illusion or the Thatcher effect is a perceptual phenomenon in which it is difficult to see localized changes in a face when this face is rotated 180 ° or is upside down, while these changes are very clearly perceived, when the face is presented the right way round .
This illusion is named for former British Prime Minister Margaret Thatcher , whose photograph was used by Peter Thompson, professor at the University of York , England in 1980 to demonstrate this illusion.

description

Thatcher.PNG

The effect can be demonstrated by two originally identical photographs, which are both rotated by 180 °, ie standing upside down. The second photograph is changed in such a way that both the eyes and the mouth are rotated by 180 ° within the image. At first glance, the two photographs hardly differ, only when the pictures are the right way up do you notice the grotesque change.

It is assumed that this illusion is caused by the specific psychological processes that play a role in human facial perception, especially in upturned faces (which occur rarely or not at all in nature). Faces are unique, although many faces look very similar in the basic pattern. There is the hypothesis that humans develop specific facial differentiation processes from birth, which are based on both the configuration of the face (spatial arrangement of the facial components; e.g. distance between eyes, distance between mouth and nose) and the details of the face Face (e.g. shape of lips , presence of earlobes). If a face is rotated by 180 °, the configuration recognition is disturbed ( the face components are not where they belong ) and, as a result, the fine-tuning by the detail recognition is also disturbed .

Neurophysiologically, the Thatcher illusion is used to temporally and spatially determine cerebral processes of facial processing. As an event-related potential , the N170 shows a shift in its latency. This suggests that inverting a face image makes it difficult to neural processing.

This illusion does not occur in people who have certain forms of prosopagnosia , a cognitive disorder in which facial perception is abnormal, usually following brain injury or related illness.

See also

Individual evidence

  1. ^ P. Thompson: Margaret Thatcher: A new illusion. (PDF; 124 kB). In: Perception. Volume 9, No. 4, 1980, pp. 483-484. (engl.)
  2. ↑ Animated example of the Thatcher illusion

literature

  • CC Carbon, H. Leder: When feature information comes first! Early processing of inverted faces. In: Perception. Volume 34, No. 9, 2005, pp. 1117-1134.
  • W. Sjoberg, JD Windes: Recognition times for rotated normal and 'Thatcher' faces. In: Perceptual and Motor Skills. Volume 75, No. 3, Pt 2, 1992, pp. 1176-1178.
  • F. Stuerzel, L. Spillmann : Thatcher illusion: dependence on angle of rotation. In: Perception. Volume 29, No. 8, 2000, pp. 937-942.
  • MB Lewis: Thatcher's children: Development and the Thatcher illusion. In: Perception. Volume 32, No. 12, 2003, pp. 1415-1421.
  • H. Rouse, N. Donnelly, JA Hadwin, T. Brown: Do children with autism perceive second-order relational features? The case of the Thatcher illusion. In: J Child Psychol Psychiatry. Volume 45, No. 7, 2004, pp. 1246-1257.
  • CC Carbon, T. Grüter, JE Weber, A. Lueschow: Faces as objects of non-expertise: Processing of Thatcherised faces in congenital prosopagnosia. In: Perception. Volume 36, No. 11, 2007, pp. 1635-1645.
  • CC Carbon, SR Schweinberger, JM Kaufmann, H. Leder: The Thatcher Illusion seen by the brain: An event-related brain potentials study. In: Cognitive Brain Research. Volume 24, No. 3, 2005, pp. 544-555.