August 2010
Volume 10, Issue 7
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2010
The Ebbinghaus Illusion as a function of age: complete psychometric functions
Author Affiliations
  • Laurence Thelen
    Department of Psychology, University of Stirling, Scotland, UK
  • Roger Watt
    Department of Psychology, University of Stirling, Scotland, UK
Journal of Vision August 2010, Vol.10, 487. doi:10.1167/10.7.487
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      Laurence Thelen, Roger Watt; The Ebbinghaus Illusion as a function of age: complete psychometric functions. Journal of Vision 2010;10(7):487. doi: 10.1167/10.7.487.

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Abstract

In the Ebbinghaus illusion the visually perceived size of circles is affected by contrast with the size of neighbouring circles. Children under 6 years are thought to show little or no illusion. We have collected data for groups of children of ages 4 to 9. Each participant was shown a series of images of a pair of target circles: one target circle was surrounded by larger circles; the other by smaller. The relative size of the two target circles was varied and participants were asked which was the larger circle. The proportion of trials when the target circle surrounded by the larger circles was selected, was plotted as a function of target cirlce size. Normally, one would take the point where this function crossed 50% to be a measure of the illusion. However, we have found that participants up to age 6 have a tendency to report on a proportion of trials the target circle surrounded by the larger ones, irrespective of the size of the target circle itself. This suggests visual crowding in these age groups: the occasional intrusion of surround circles into the judgement. When one allows for this, then there is no further difference between any age groups and adults.

Thelen, L. Watt, R. (2010). The Ebbinghaus Illusion as a function of age: complete psychometric functions [Abstract]. Journal of Vision, 10(7):487, 487a, http://www.journalofvision.org/content/10/7/487, doi:10.1167/10.7.487. [CrossRef]
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