title: The force of symmetry revisited: symmetry-to-noise ratios regulate (a)symmetry effects.
abstract: Freyd and Tversky's [Am. J. Psychol. 97 (1984) 109] data suggested that human observers tend to overestimate relatively high levels of symmetry (symmetry effect), and tend to underestimate relatively low levels of symmetry (asymmetry effect). However, on the basis of their holographic approach to visual regularity, van der Helm and Leeuwenberg [Psychol. Rev. 103(3) (1996) 429] predicted that, at any level of symmetry, both symmetry and asymmetry effects may occur as a consequence of correct estimates of symmetry-to-noise ratios. This prediction was tested in two experiments, with tasks and stimuli similar to those in Freyd and Tversky's study. First, subjects had to judge whether a noisy symmetry is more similar to a slightly more symmetrical variant or to a slightly less symmetrical variant. Second, for every pair of stimuli in such a triadic comparison, subjects had to judge which stimulus is the more symmetrical one. The results from both experiments show that the occurrence of (a)symmetry effects indeed depends on symmetry-to-noise ratios.
authors.affiliation: Nijmegen Institute for Cognition and Information, University of Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands. arpad.csatho@aok.pte.hu
authors.forename: Arpád
authors.initials: A
authors.lastname: Csathó
authors.forename: Gert
authors.initials: G
authors.lastname: van der Vloed
authors.forename: Peter A
authors.initials: PA
authors.lastname: van der Helm
mesh_terms: D000293:Adolescent; D000328:Adult; D001307:Auditory Perception / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008027:Light; D009622:Noise; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*