Abstract: Subitizing, the fast and accurate perception of up to about 3 or 4 objects, reflects a basic capacity of numerical representation of organism. It used to be considered as a parallel preattentive process. Recently, some studies found that subitizing, like counting, required attention resources. However, the attention resource hypothesis could not powerfully explain the discontinuity between subitizing and counting. To disentangle the confusion, this review summarized recent studies on visuo-spatial working memory, and put forward a new perspective of the cognitive mechanism of subitizing based on the similarity between subitizing and visuo-spatial working memory. We argued that visuo-spatial working memory capacity limited the number of objects we could accurately perceive at a time, while attention determined what information would enter into visuo-spatial working memory.

Key words: subitizing, cognitive mechanism, attention, visuo-spatial working memory