Persisting activation in voluntary task switching: it all depends on the instructions.

We tested the hypothesis that persisting activation from a previous task execution does not contribute to the switch cost in voluntary task switching. We reasoned that voluntary task switching requires the selection of random task sequences, which necessitates the active inhibition of previously executed tasks. The asymmetric switch cost was used as a marker for persisting activation. Participants switched voluntarily between color naming and word naming. One group was instructed to select unpredictable task sequences. The other group was not instructed to do so. When participants were instructed to be unpredictable, no asymmetric switch cost was observed. When participants were not instructed to be unpredictable, an asymmetric switch cost was observed. We conclude that the amount of persisting activation in voluntary task switching is limited and that the switch cost in voluntary task switching reflects the time needed for reconfiguring the cognitive system from one task to another rather than the time needed to compensate for persisting activation.