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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.