Treder M S, van der Helm P A, 2006, "Breaking up symmetry in depth" Perception 35 ECVP Abstract Supplement
Breaking up symmetry in depth
M S Treder, P A van der Helm
Symmetry detection is at its best when it can integrate symmetry pairs into a single object. The purpose of this study was to probe the symmetry detection mechanism by investigating the effect of redistributing parts of a symmetric pattern in depth. Subjects were asked to discriminate symmetric patterns from random-dot patterns. Stimuli consisted of three depth layers and were viewed through shutter glasses. The deepest layer always contained 'noise' (randomly positioned dots) and served as background for the two top layers which together formed either another noise pattern or a symmetric pattern. The noisy background layer was used to control task difficulty and to stimulate the subjects to make effective use of binocular disparity, as depth segregation of the stimulus could be used to separate noise from symmetry. The symmetric pattern was either presented in one of the two top layers or spread across these layers, by using a number of different manipulations. Presentation time was varied to explore when and how the symmetry detection mechanism reacts to stereoscopic depth information. Preliminary data suggest that depth information is available at presentation times of 300 ms or more, and that breaking up symmetry in depth interferes with the detection of symmetry.
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