FMRI provides new constraints on theories of the Psychological Refractory Period

We used functional magnetic resonance imaging (fMRI) to investigate the psychological refractory period (PRP), the delay in the response to the second of two tasks occurring in immediate succession (Pashler, 1994). Consistent with prior work on the PRP, we found that when two visual-manual tasks were presented within an interval of 100ms of each other, the second response was delayed on the order of 500ms, compared with a condition when the two tasks were separated by 1500ms. Surprisingly, there was virtually no increase in brain activation associated with the short interval compared with the long interval condition, in brain regions postulated to be important for executive functions. These data suggest that passive queuing, rather than active monitoring, occurs during the PRP. Introduction Participants in today's fast-paced society often find themselves wishing that there were 48 hours in a day, or that they could do two things at a time. Yet carrying out two tasks concurrently is almost as difficult as finding 48 hours in a day. The psychological literature shows that dual-task interference (Kahneman, 1973) is most striking when the processing for the two tasks overlaps at the response selection stage, when percepts are