On the electrophysiological evidence for the capture of visual attention

Abstract

The presence of a salient distractor interferes with visual search. According to the salience-driven selection hypothesis, this interference is because of an initial deployment of attention to the distractor. Three event-related potential (ERP) findings have been regarded as evidence for this hypothesis: (a) salient distractors were found to elicit an ERP component called N2pc, which reflects attentional selection; (b) with target and distractor on opposite sides, a distractor N2pc was reported to precede the target N2pc (N2pc flip); (c) the distractor N2pc on slow-response trials was reported to occur particularly early, suggesting that the fastest shifts of attention were driven by salience. This evidence is equivocal, however, because the ERPs were noisy (b, c) and were averaged across all trials, thereby making it difficult to know whether attention was deployed directly to the target on some trials (a, b). We reevaluated this evidence using a larger sample size to reduce noise and by analyzing ERPs separately for fast- and slow-response trials. On fast-response trials, the distractor elicited a contralateral positivity (PD)-an index of attentional suppression-instead of an N2pc. There was no N2pc flip or early distractor N2pc. As it stands, then, there is no ERP evidence for the salience-driven selection hypothesis.