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Symmetry 2018, 10(6), 220;

Spatiotemporal and Luminance Contrast Properties of Symmetry Perception

Department of Psychology, University of Stirling, Stirling FK9 4LA, Scotland, UK
Author to whom correspondence should be addressed.
Received: 11 May 2018 / Revised: 5 June 2018 / Accepted: 11 June 2018 / Published: 14 June 2018
(This article belongs to the Special Issue Symmetry-Related Activity in Mid-Level Vision)
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Recent studies have shown that limiting the lifetime of pattern elements improves symmetry detection, potentially by increasing the number of element locations. Here, we investigate how spatial relocation, luminance contrast modulation and lifetime duration of elements affect symmetry perception in dynamic stimuli. Stimuli were dynamic dot-patterns containing varying amounts of symmetry about a vertical axis. Symmetrical matched-pairs were: (i) relocated to multiple successive, but random locations (i.e., multiple locations condition); (ii) relocated between the same two locations (i.e., two locations condition); (iii) not, relocated, but their luminance contrast was modulated at different temporal frequencies (i.e., one location condition), and (iv) not relocated, but a single pattern was presented at full contrast (i.e., static condition). In the dynamic conditions, we varied the elements’ lifetime duration and temporal frequency of contrast modulation. We measured symmetry detection thresholds using a two-interval forced choice procedure. Our results show improved performance for the multiple locations condition compared to two-location and static conditions, suggesting a cumulative process whereby weak symmetry information is integrated by spatiotemporal filters to increase overall symmetry signal strength. Performance also improved for the static, contrast modulated patterns, but this was explained by a reduction in perceived density. This suggests that different mechanisms mediate symmetry detection in dynamic stimuli and static contrast modulated patterns. View Full-Text
Keywords: temporal frequency; dynamic flicker; luminance contrast; visual perception; psychophysics temporal frequency; dynamic flicker; luminance contrast; visual perception; psychophysics

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Sharman, R.J.; Gheorghiu, E. Spatiotemporal and Luminance Contrast Properties of Symmetry Perception. Symmetry 2018, 10, 220.

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