Top-down search strategies determine attentional capture in visual search: Behavioral and electrophysiological evidence

To investigate how attentional capture in visual search is affected by generalized top-down search strategies, ERPs and behavioral performance were measured in two experiments where spatially nonpredictive color singleton cues preceded visual search arrays that contained one of two equally likely color singletons. When both singletons served as targets, irrelevant-color singleton cues produced behavioral attentional capture effects and elicited an N2pc component, indicative of a singleton search mode. When responses were required to only one of the two color singletons, the same cues no longer elicited behavioral spatial cuing effects, and the N2pc to these cues was attenuated and delayed, in line with the hypothesis that search was now guided by a feature-specific search strategy. Results demonstrate that the ability of visual singleton stimuli to capture attention is not simply determined by their bottom-up salience, but strongly modulated by top-down task sets.