Attentional processing of multiple targets and distractors.

We assessed the functioning of attention when multiple relevant objects are intermingled with multiple distractors, measuring two electrophysiological subcomponents of the N2pc that have been associated, respectively, with target selection and distractor suppression: the target negativity (Nt) and the distractor positivity (Pd). To this aim, we orthogonally manipulated the number of targets and distractors in an enumeration task. The Nt was modulated by target, but not distractor numerosity, suggesting that an increase in target numerosity leads to an increase in attentional resources needed to form individual representations of the targets. In contrast, the number of distractors did not differentially alter the Pd. We hypothesize that distractors sharing similar visual features can be processed (and possibly suppressed) as a set, without the need for individuation.