Detection of visual symmetries

Abstract

This paper reviews empirical evidence for the detection of visual symmetries and explanatory theories and models of symmetry detection. First, mirror symmetry is compared to other types of symmetry. The idea that symmetry detection is preattentive is then discussed and other roles that attention might play in symmetry detection are considered. The major part of the article consists of a critical examination of the extensive literature about the effects on symmetry detection of several major factors such as the orientation of the symmetry axis, the location of the stimulus in the visual field, grouping, and perturbations. Constraints on plausible models of symmetry detection are derived from this rich database and several proposals are evaluated against it. As a result of bringing this research together, open questions and remaining gaps to be filled by future research are identified.

Peripheral Contour Grouping and Saccade Targeting: The Role of Mirror Symmetry

“…Nevertheless, after we found no effects of symmetry on two out of the three saccade metrics of central interest, we decided to test whether vertical mirror symmetry would yield more or larger effects due to its potentially higher saliency. The trend across the symmetry detection literature is that vertical mirror symmetry is easier to detect than horizontal mirror symmetry, although not all studies individually show a difference between these two axes (see [45] for a review). We ran two concurrent experiments.…”

Mirror-image relations in category learning

“…Concerning the former of these results, the difficulty to learn the classification of patterns that are mirror-symmetric counterparts of each other stands in marked contrast to the efficiency and speed of detecting bilaterally symmetric shapes (see Wagemans, 1996). Owing to this efficiency bilateral symmetry relations have been repeatedly assigned to the class of stimulus properties that can be detected pre-attentively (e.g., Barlow and Reeves, 1979;Wolfe and Friedman-Hill, 1992;Locher and Wagemans, 1993).…”

Asymmetry for Symmetry: Right-Hemispheric Superiority in Bi-Dimensional Symmetry Perception

“…In fact, several models have been proposed in the attempt to explain how symmetry is detected and analyzed by the brain (e.g., [1][2][3][4][5][6][7]). Among the most acknowledged models, the perceptual rules proposed by Gestalt psychologists suggested that our preference for symmetric configurations ("symmetry bias") could be considered as a consequence of the perceptual preference for regularity and balance, compared to randomness and imbalance, by the human visual system.…”

“…In other words, it has been suggested that the preferential activation of two homologue areas in the left and right hemispheres is the basis for the automatic detection of symmetry in the physical world. In this "callosal hypothesis", the detection of symmetry may be favored by the activity of two specular areas in the left and right halves of the brain, which are connected by means of the fibers constituting the corpus callosum [1,2,[14][15][16]. In this frame, it has been suggested that both the left and the right hemispheres are capable of low-level perceptual processing, and that hemispheric asymmetries arise at later stages of visual processing, in associative areas representing the two sides of visual space [17].…”