The spatial mechanisms mediating symmetry perception. 1997

S C Dakin, and R F Hess
McGill Vision Research, Department of Ophthalmology, Montreal, Quebec. scdakin@astra.vision.mcgill.ca

This paper examines the role of spatial frequency and orientation tuned channels in the perception of visual symmetry. Subjects discriminated between band-pass filtered, white noise textures that either did or did not contain vertical bilateral symmetry (VBS, i.e., around a vertical midline) as a function of the spatial phase disruption imposed on the images. Resistance to phase noise is largely scale-invariant for isotropically filtered images, but horizontally filtered images are consistently more noise-resistant than vertical. However, when stimuli are rotated through 90 deg (horizontal bilateral symmetry, HBS) performance is better with vertically filtered images suggesting a general advantage for orientations orthogonal to the axis of symmetry. At these orientations symmetry may be signaled directly by clusters of features along the axis. Our data further suggest that the established disadvantage for HBS may be attributable to an over-reliance on the output of horizontal filters. We compare models which exploit feature clustering around the axis by measuring the co-alignment in the output of oriented filters. Models using filters oriented orthogonal to the axis of symmetry predict the psychophysical performance for isotropic patterns and for patterns filtered orthogonal to the axis. For patterns filtered parallel to the axis, our data suggest that visual attention may play a role.

UI MeSH Term Description Entries
D008297 Male Males
D008433 Mathematics The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Mathematic
D008960 Models, Psychological Theoretical representations that simulate psychological processes and/or social processes. These include the use of mathematical equations, computers, and other electronic equipment. Model, Mental,Model, Psychological,Models, Mental,Models, Psychologic,Psychological Models,Mental Model,Mental Models,Model, Psychologic,Psychologic Model,Psychologic Models,Psychological Model
D010364 Pattern Recognition, Visual Mental process to visually perceive a critical number of facts (the pattern), such as characters, shapes, displays, or designs. Recognition, Visual Pattern,Visual Pattern Recognition
D010775 Photic Stimulation Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity. Stimulation, Photic,Visual Stimulation,Photic Stimulations,Stimulation, Visual,Stimulations, Photic,Stimulations, Visual,Visual Stimulations
D011601 Psychophysics The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship. Psychophysic
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012399 Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Clinorotation,Clinorotations,Rotations
D014796 Visual Perception The selecting and organizing of visual stimuli based on the individual's past experience. Visual Processing,Perception, Visual,Processing, Visual

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