The Formation of Symmetrical Gestalts Is Task-Independent, but Can Be Enhanced by Active Regularity Discrimination.

Alexis D J Makin,Amie Morris,Giulia Rampone,Marco Bertamini

doi:10.1162/jocn_a_01485

Alexis D J Makin, Amie Morris + Show 2 more

Open Access

https://doi.org/10.1162/jocn_a_01485

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Abstract

The brain can organize elements into perceptually meaningful gestalts. Visual symmetry is a useful tool to study gestalt formation, and we know that there are symmetry-sensitive regions in the extrastriate cortex. However, it is unclear whether symmetrical gestalt formation happens automatically, whatever the participant's current task is. Does the visual brain always organize and interpret the retinal image when possible, or only when necessary? To test this, we recorded an ERP called the sustained posterior negativity (SPN). SPN amplitude increases with the proportion of symmetry in symmetry + noise displays. We compared the SPN across five tasks with different cognitive and perceptual demands. Contrary to our predictions, the SPN was the same across four of the five tasks but selectively enhanced during active regularity discrimination. Furthermore, during regularity discrimination, the SPN was present on hit trials and false alarm trials but absent on miss and correct rejection trials. We conclude that gestalt formation is automatic and task-independent, although it occasionally fails on miss trials. However, it can be enhanced by attention to visual regularity.

Highlights

The visual brain must organize and interpret the retinal image
Amplitude is more negative at posterior electrodes when participants view regular or symmetrical patterns where corresponding elements can be grouped into an organized whole (Makin, Wilton, Pecchinenda, & Bertamini, 2012; Jacobsen & Höfel, 2003). fMRI has identified symmetry-related BOLD responses in the extrastriate cortex ( Van Meel, Baeck, Gillebert, Wagemans, & Op de Beeck, 2019; Keefe et al, 2018; Kohler, Clarke, Yakovleva, Liu, & Norcia, 2016; Sasaki, Vanduffel, Knutsen, Tyler, & Tootell, 2005; Tyler et al, 2005), and this extrastriate activity probably generates the sustained posterior negativity (SPN) (Makin et al, 2016)
There was a significant increase in P correct with every increment of PSYMM

Summary

Introduction

The visual brain must organize and interpret the retinal image. We know many rules that govern perceptual organization (Wagemans et al, 2012; Hoffman, 1998), but the circumstances under which perceptual organization happens are unclear. An ERP component called the sustained posterior negativity (SPN) provides this. Amplitude is more negative at posterior electrodes when participants view regular or symmetrical patterns where corresponding elements can be grouped into an organized whole (Makin, Wilton, Pecchinenda, & Bertamini, 2012; Jacobsen & Höfel, 2003). FMRI has identified symmetry-related BOLD responses in the extrastriate cortex ( Van Meel, Baeck, Gillebert, Wagemans, & Op de Beeck, 2019; Keefe et al, 2018; Kohler, Clarke, Yakovleva, Liu, & Norcia, 2016; Sasaki, Vanduffel, Knutsen, Tyler, & Tootell, 2005; Tyler et al, 2005), and this extrastriate activity probably generates the SPN (Makin et al, 2016). We can posit that if an SPN is recorded at the scalp, perceptual

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