Journal Article

Polygons have a small facilitatory effect on extraretinal symmetry perception

Makin, Alexis D.J., Karakashevska, Elena

2024

Overview

•The extrastriate cortex responds to visual symmetry. The extrastriate symmetry activation generates and event related potential (ERP) called the sustained posterior negativity (SPN).•The SPN indicates how the brain processes visual symmetry and constructs extraretinal representations. Some stimulus types may representations even during secondary tasks, contrary to previous beliefs.•Dot patterns and polygons were compared, revealing differences in how the brain represents symmetry.•Polygons reduced the perspective cost compared to dot patterns, affecting extraretinal representation.•Achieving view invariance is more complex than suggested, as perspective cost was not reduced to zero in any case. Symmetrical objects only project a symmetrical image onto the retina when viewed from certain angles. Previous work has investigated the ERP response to visual symmetry in frontoparallel and perspective views. When participants are attending to regularity, the ERPs are the same. When participants are attending to colour, the response to perspective symmetry is reduced. We term this reduction ‘perspective cost’. We predicted that perspective cost would be lessened if the stimuli were polygons rather than dot patterns. This prediction was confirmed in a new experiment. This result suggests some stimuli may support automatic 3D interpretation better than others. However, the facilitatory effect of polygons was relatively small, and perspective cost was not eliminated. Furthermore, this study also revealed that attention to symmetry is not always sufficient to eliminate perspective cost.

• Publisher: Elsevier Inc,Elsevier Limited,Elsevier
• Subject: Age / Asymmetry / EEG / Event-related potentials / Perceptual constancy / Polygons / Sustained posterior negativity / Symmetry / View invariance / Visual perception