Metacontrast masking of symmetric targets

Visual shape perception is affected by masking. One type of masking called metacontrast masking involves a briefly flashed target and a spatially adjacent mask that follows at varying stimulus onset asynchronies (SOAs). The strength of masking is measured by the decrease of the target’s visibility as a function of SOAs. Aydin (2021) demonstrated that a masking function produced depends on the contrast polarity relationship between the target and mask stimuli. The typical U-shaped function is only present for same-polarity stimuli. This study aims to replicate and extend Aydin's findings by examining symmetry in a metacontrast masking paradigm. As in the original study, we used asymmetrical discs with contour deletion on either the left or the right. Additionally, we used new symmetric stimuli, including discs with bilateral contour deletions, symmetric and asymmetric polygons, and complex “butterfly” stimuli with or without vertical symmetry. It is hypothesised that we will replicate the characteristic U-shaped function at intermediate SOAs, and a facilitation effect at 0 ms. By employing these stimuli, this research intends to explore how symmetry influences masking effects. Symmetry is a prominent feature of the visual world and it plays a role in many higher-level processes of visual perception. Investigating symmetry adds complexity to our understanding of masking phenomena and may reveal novel insights into visual perception mechanisms. By replicating and extending Aydin's findings and investigating new stimuli, this study contributes to the growing body of literature on metacontrast masking and its implications for understanding visual perception phenomena.