The benefit of task rhythm for switching and interruption performance

Edita Poljac, Peter Desain & Harold Bekkering

Radboud University Nijmegen, the Netherlands

Recently, Jones et al. (2002) have shown that rhythmically expected tones were processed faster by listeners than rhythmically unexpected ones. It seems that the execution of an auditory task (e.g., comparative pitch judgments) profits from temporal expectancies of the stimulus rhythm. In the present study, we applied this concept of performance benefit of rhythmical expectations to the area of executive control. Within the literature in this domain, two interesting phenomena have been reported with regard to sequential tasks. When a sequence of trials is being interrupted, and a switch to a different task or a continuation of the same task is being required, a switch or restart cost is present on the first trial after the interruption. Also in our lab, we found significant performance costs (increase in reaction times and error rates) due to switching and restarting color and shape matching tasks. The tasks were presented repeatedly in a multiple-trial design, in which a run of trials followed an initial (explicitly) cued trial. Gopher, Armony, and Greenshpan (2000) suggested that performing a run of trials of the same task enables the development of a task rhythm. Every time this rhythm is interrupted, the system needs some extra time to generate the first response of the following run of trials. To test the involvement of task rhythm in task switching and task resumption performance, we conducted two experiments. In Experiment 1, we examined whether requiring a task switch or a task resumption on rhythmically expected moments reduced switch and restart costs. The task rhythm was induced here by a fixed intertrial interval (ITI). The critical ITIs were rhythmical or not rhythmical. We expected to find a reduction in switch and restart costs for the rhythmical critical ITIs. Experiment 2 was the control experiment, in which the task rhythm was irregular. Here, we expected to find no difference in performance costs.