Brain dynamics of attention and working memory engagement in subitizing.

This study addressed the engagement of attention and working memory, as inferred from electrophysiological measurements, in the processing of small sets of objects. We recorded N2pc and CDA, two lateralized components of the EEG signal associated respectively with individuation and visual working memory, while participants enumerated a variable number (1-9) of uniquely colored targets among distractors. Behavioral results showed a clear subitizing effect, with lower error rates for smaller (1-3 targets) than larger sets. ERP results showed that both N2pc and CDA amplitudes increased as a function of target numerosity up to approximately three targets. However, individual differences in the enumeration efficiency were correlated only with the individual variation in the N2pc modulations. The results suggest that the constraints of the attentional individuation system play a significant role in the occurrence of the subitizing phenomenon.