Recent studies in the perception of numerosity have indicatedthat subitizing (the rapid and accurate enumeration of smallquantities) requires attention. We present a novel computa-tional model of enumeration in which attention unifies dis-tinct processes of numerosity approximation, subitizing, andexplicit counting. We demonstrate how this model accountsfor both the reaction time results from the subitizing literatureand the effects of attentional load on subitizing accuracy.
