Aurore Maloh^1,2 (), Lara Pierce¹, Peter J. Kohler^1,2; ¹Department of Psychology, York University, ²Centre for Vision Research, York University

Visual symmetry is a fundamental property of natural environments and plays an important role in object recognition and perceptual organization. In adults, brain imaging studies have demonstrated robust responses to reflection symmetry in several areas of the visual cortex, using dot patterns with one or more axes of reflection. Another approach has used the wallpaper groups, 17 regular textures that comprise the complete set of possible symmetries in the 2D plane. Each wallpaper group contains a unique combination of fundamental symmetries, including reflection and rotation. The visual cortex responds robustly to combinations of symmetries in the wallpaper groups, with reflection symmetry typically producing stronger responses than rotation symmetry. The current study used the wallpaper groups to record brain responses to reflection (PMM) and rotation (P4) symmetry from 18 infants aged 2-8 months using high-density electroencephalography (EEG) with a Steady-State Visual Evoked Potentials (SSVEPs) paradigm. Infants viewed full-field (24º/visual angle) wallpaper textures from the PMM and P4 groups alongside matched phase-scrambled control images that preserved low-level visual properties while removing global structure. This paradigm isolates symmetry-specific responses and low-level responses driven by changes in contrast at each image update. Results revealed robust image update responses for PMM and P4, indicating that infants were generally equally willing to look at the screen for both conditions. We also found adult-like responses to reflection symmetry in infants, but rotation symmetry produced responses that were much less adult-like, if measurable at all. To our knowledge, these are the first measurements of brain responses to symmetry in early infancy. Our results suggest a learned component of symmetry processing, and hint that infants may learn to see reflection earlier than rotation, possibly due to differential exposure during the initial months of life.