Symmetry Perception and Psychedelic Experience
Symmetry June 30, 2023 Alexis D. J. Makin, Marco Roccato, Elena Karakashevska et al. 19 citations
A review of symmetry perception synthesizes findings from psychophysics, neuroscience, and aesthetics. Over a century of psychophysical studies are joined by recent functional MRI and EEG evidence showing that regular visual patterns—reflection symmetry, Glass patterns, and wallpaper groups—activate the extrastriate visual cortex, producing an event-related potential called sustained posterior negativity (SPN). SPN amplitude scales with the degree of visual regularity and occurs regardless of attention. Some symmetry detection appears automatic, unconscious, and pre-attentive, possibly hardwired, which may explain its aesthetic appeal. Symmetry and fractal geometry also appear in hallucinations induced by DMT and visual flicker, suggesting the extrastriate cortex can generate symmetrical representations spontaneously without external stimuli.