Unexpected abrupt onsets can override a top-down set for color.

A substantial literature supports the contention that the involuntary allocation of spatial attention to salient stimuli is contingent on the top-down goals of the observer. However, recent studies suggest that stimuli that violate expectations built up through experience can override top-down set, resulting in cognitively impenetrable, involuntary shifts of spatial attention. The present studies provide a strong test of this hypothesis by manipulating the frequency of presentation of salient, irrelevant, stimuli in spatial cuing and rapid serial visual presentation (RSVP) paradigms. Experiments 1, 2, and 3 found that for targets defined by color, infrequent, uninformative onset precues produce evidence of capture, but that for targets defined by onset, infrequent color singleton precues do not. Experiment 4 provides strong converging evidence for the ability of infrequent onsets to override a top-down set for color; when monitoring an RSVP stream for a colored target, an infrequent onset in the periphery produced a decrement in target report indicative of attentional capture. Together, the results suggest that infrequent onsets represent a special class of stimuli that can produce involuntary shifts of spatial attention that are cognitively impenetrable.