Global shape versus local feature: an angle illusion

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17 Citations (Scopus)


We have shown previously that the precision of angle judgments depends strongly on the global stimulus configuration: discrimination thresholds for angles that form part of isosceles triangles are up to 3 times lower than for those that form part of scalene triangles [Kennedy, G. J., Orbach, H. S., & Loffler, G. (2006). Effects of global shape on angle discrimination. Vision Research, 46(8–9), 1530–1539]. Here, we investigated whether or not the perceived size of an angle (accuracy) is also affected by the overall shape of which it forms a part. Observers compared the relative sizes of angles contained in isosceles triangles with those of angles in scalene triangles and points of subjective equality were determined. For a reference angle of 60°, angles embedded in isosceles triangles were judged to be on average 14° larger than angles embedded in scalene triangles. This result is largely independent of the reference angle, triangle orientation and triangle size.

Original languageEnglish
Pages (from-to)1281-1289
Number of pages9
JournalVision Research
Issue number11
Publication statusPublished - 1 May 2008


  • angle judgement
  • vision sciences


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