Involuntary attentional capture is determined by task set: evidence from event-related brain potentials

To find out whether attentional capture by irrelevant but salient visual objects is an exogenous bottom-up phenomenon, or can be modulated by current task set, two experiments were conducted where the N2pc component was measured as an electrophysiological marker of attentional selection in response to spatially uninformative color singleton cues that preceded target arrays. When observers had to report the orientation of a uniquely colored target bar among distractor bars (color task), behavioral spatial cueing effects were accompanied by an early cue-induced N2pc, indicative of rapid attentional capture by color singleton cues. In contrast, when they reported the orientation of target bars presented without distractors (onset task), no behavioral cueing effects were found and no early N2pc was triggered to physically identical cue arrays. Experiment 2 ruled out an alternative interpretation of these N2pc differences in terms of distractor inhibition. These results do not support previous claims that attentional capture is initially unaffected by top-down intention, and demonstrate the central role of task set in involuntary attentional orienting.