Attentional modulation of size contrast

A test circle surrounded by smaller context circles appears larger if presented in isolation, whereas a test circle surrounded by large context circles is seen as smaller than in isolation. Two experiments are reported indicating that this phenomenon, the Ebbinghaus illusion, depends on whether subj...

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Bibliographic Details
Published inThe Quarterly journal of experimental psychology. A, Human experimental psychology Vol. 45; no. 4; p. 529
Main Author Shulman, G L
Format Journal Article
LanguageEnglish
Published England 01.11.1992
Subjects
Attention
Color Perception
Humans
Illusions
Size Perception
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ISSN0272-4987
DOI10.1080/14640749208401332

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Summary:A test circle surrounded by smaller context circles appears larger if presented in isolation, whereas a test circle surrounded by large context circles is seen as smaller than in isolation. Two experiments are reported indicating that this phenomenon, the Ebbinghaus illusion, depends on whether subjects are attending to the context circles. Subjects first saw a reference circle and then a briefly presented (150 msec) test circle. Their task was to determine whether the test circle was larger or smaller than the reference. The test circle was surrounded by smaller context circles of one colour arrayed along a horizontal axis centred on the test, and larger context circles of a different colour arrayed along a vertical axis centred on the test. Subjects judged both the size of the test and the colours of either the small or large context circles. Perceived test size changed systematically, depending on which context circles were task-relevant.
ISSN:0272-4987
DOI:10.1080/14640749208401332