Neural predictors of within-subject fluctuations in attentional control.

Whether salient objects automatically capture attention has long been the subject of considerable controversy. A possible resolution, investigated in this functional magnetic resonance imaging (fMRI) study, is that observers vacillate between periods when attention capture is robust and when it is minimal. Human observers searched static displays for a target circle among nontarget squares; an irrelevant color singleton distractor appeared on 50% of trials. Behavioral results showed a distraction effect in which response times to distractor-present trials were slower than for distractor-absent trials. fMRI results confirmed that this distraction effect not only fluctuated within experimental sessions, but the momentary degree of distraction could be predicted in advance by pretrial activity in middle frontal gyrus. A second experiment ruled out an alternative account by which participants achieved resistance to capture by trading off search efficiency. Together, these data reveal that observers frequently exert the capacity to resist attentional distraction, although they do not to sustain this capacity for long periods of time.