Parallel visual processes in symmetry perception: Normality and pathology

Mirror symmetry is one of those regularities for which the visual system se ems to have developed a special sensitivity. It is detected robustly and ef ficiently in a single glance, suggesting that the basic processes do not pe rform a serial, pointwise comparison of structural elements but rather oper ate in parallel. Psychophysical evidence relating to the processing mechani sms will be reviewed. Although the focus will be on symmetry perception in normal vision, interesting findings on symmetry perception in observers wit h deficient vision (e.g., retinitis pigmentosa, visual hemineglect) will al so be touched upon briefly.