Contextual effects on symmetry perception (360G-Wellcome-207182_Z_17_Z)

The human visual system is tasked with extracting and recognising objects and surfaces from the feature-rich backgrounds in which they are embedded. Most objects in natural scenes appear symmetric. Symmetry plays an important role in perceptual organisation, particularly in figure-ground segregation (symmetry is a property of the ‘figure’ rather than the ‘ground’). If this is the case then the visual system should be able to easily segment symmetry from background noise. Thus, this project will investigate the mechanisms responsible for contextual modulation of symmetry by examining spatial and temporal properties of centre-surround interactions in symmetry processing. We will examine how texture-surrounds influence the perception of a symmetrical central-target, as well as how symmetrical surrounds change the appearance of a noise central-target. We predict that symmetry detection will be impaired by a noise surround, and a symmetrical surround will make a noise centre appear more symmetric. By studying contextual effects on symmetry perception, we can gain insight into the role of symmetry in figure-ground segregation and the spatial and temporal limitations of these mechanisms in normal vision. Furthermore, it allows to predict how these mechanisms will be affected in an aging visual system and in abnormal processing of context (schizophrenia, autism).