Are Hierarchical Representations in Working Memory Hemisphere-Separated?

In previous studies (Brady, Alvarez, 2011) it was shown that representations in visual working memory (VWM) are the integration between individual memories and ensemble summary statistics. In this study, we investigate the question of whether the origin of these representations connects with the mechanism of spatial pooling in visual cortex. We presented to participants two sets of three circles with different mean sizes in two different hemifields. Participants should memorize all six target circles and report a random one after a delay. We found a strong bias toward the hemifield mean which reveals that, first, items do not store independently from each other in VWM. Secondly, close items more influenced each other than far elements (as spatial pooling predicts). We did not find differences between horizontal and vertical arrangement of stimuli which suggest that integration of individual representations occurs mostly with local, not global ensemble summaries. All the results support hierarchical encoding theory but cannot be explained by other theories of VWM.