The distractor positivity (Pd) signals lowering of attentional priority: evidence from event-related potentials and individual differences

We investigated the effects of task demands and individual differences on the allocation of attention. Using the same stimuli, participants indicated the orientation of a line contained in a shape singleton (identification task) or the presence of singletons (detection task). Shape singletons in the identification task elicited a contralateral negativity (N2pc) whereas shape singletons in the detection task elicited a contralateral positivity (Pd). We suggest that the reduction of attentional priority of a salient stimulus, reflected by the Pd, occurred more rapidly with the less demanding detection task. Further, fewer distractible participants showed a larger N2pc to lateral color distractors than highly distractible participants. We suggest that highly distractible participants developed compensatory mechanisms to suppress distracting stimuli.