No-go trials in task switching: effects on the task-set and task-space level.

A common marker for inhibition processes in task switching are n - 2 repetition costs. The present study aimed at elucidating effects of no-go trials on n - 2 repetition costs. In contrast to the previous studies, no-go trials were associated with only one of the three tasks in the present two experiments. High n - 2 repetition costs occurred if the no-go task had to be executed in trial n - 2, irrespective of whether a response had to be withheld or not. In contrast, no n - 2 repetition costs were visible if the other two tasks were relevant in n - 2. Whereas this n - 2 effect was unaffected by whether participants could reliably exclude a no-go trial or not, effects of no-gos in trial n were determined by this knowledge. The results differ from effects of no-go trials that are not bound to a specific task. It is assumed that the present no-go variation exerted its effect not on the response level, but on the level of task sets, resulting in enhanced salience of the no-go task that leads to higher activation and, as a consequence, to stronger inhibition. The dissociation of the effects on no-gos in trials n - 2 and n as a function of foreknowledge suggests that the balance between activation and inhibition is shifted not only for single trials and tasks, but for the whole task space.