Chunking, Attraction, Repulsion, and Ensemble Effects Are Ubiquitous in Visual Working Memory.

What happens when there are many different objects that must be maintained simultaneously in visual working memory? Prominent models focus largely on individual objects in describing memory limits: e.g., claims that we can remember only a fixed number of items, or that a single resource limit describes the cost of holding additional items. While some acknowledge interactions between items, these interactions are not given a prominent role in most models. Here we show that instead of items being represented independently, the visual display is always compressed by utilizing clusters of items and the gist of the display. We reanalyze data from 11 previously available datasets (comprising 137,986 trials in total). We find strong evidence for non-independent representations, including chunking and use of the 'gist' of the display, which is present in nearly every study at every set size. We then present a model for understanding this chunking and the resulting systematic biases (e.g., items attracting and repelling one another) based on psychophysical similarity. Overall, this work provides strong evidence that in order to understand visual working memory, we need to consider how our memory system takes advantage of the relationship between items. This is in contrast to the way the majority of the field studies visual working memory and suggests a major paradigm shift is required to think of memory in terms of clusters, chunks, and gist rather than in terms of independent items.