Unit of Visual Working Memory: A Boolean Map Provides a Better Account Than an Object Does

What is the unit of visual working memory? This is a question fundamental to our understanding of how the human mind represents the visual world. Here, I challenge the "object-based" account and argue that the unit of visual working memory is better defined by the concept of a "Boolean map." A Boolean map emphasizes the critical role of spatial structure and has been used to characterize the conscious access in attentional processing. Experiments 1-3 show that, for both overall capacity and access to stored information, there is a 0 same-object advantage for different-part features but a significant same-Boolean-map advantage for multiple same-feature objects. Experiments 4-9 support that multiple orientations, but not multiple colors or shapes, can be memorized together as a "spatial structure," and this uniqueness of orientations is attributed to a mimicking strategy (i.e., using the spatial structure of Boolean map to mimic the feature orientation). In summary, a Boolean map offers a better account for the unit of visual working memory than an object does.