Hierarchical encoding in visual working memory: ensemble statistics bias memory for individual items
Influential models of visual working memory treat each item to be stored as an independent unit and assume there are no interactions between items. However, real-world displays have structure, providing higher-order constraints on the items to be remembered. Even displays with simple colored circles contain statistics, like the mean circle size, that can be computed by observers to provide an overall summary of the display. Here we examine the influence of such an ensemble statistic on visual working memory. We find evidence that the remembered size of each individual item is biased toward the mean size of the set of items in the same color, and the mean size of all items in the display. This suggests that visual working memory is constructive, encoding the display at multiple levels of abstraction and integrating across these levels rather than maintaining a veridical representation of each item independently.