Parallel visual processes in symmetry perception: Normality and pathology

Mirror symmetry is one of those regularities for which the visual system seems to have developed a special sensitivity. It is detected robustly and efficiently in a single glance, suggesting that the basic processes do not perform a serial, pointwise comparison of structural elements but rather operate in parallel. Psychophysical evidence relating to the processing mechanisms will be reviewed. Although the focus will be on symmetry perception in normal vision, interesting findings on symmetry perception in observers with deficient vision (e.g., retinitis pigmentosa, visual hemineglect) will also be touched upon briefly. This revised version was published online in July 2006 with corrections to the Cover Date.