Is it harder to switch among a larger set of tasks?

This is the author accepted manuscript. The final version is available from American Psychological Association via the DOI in this record.When stimuli afford multiple tasks, switching among them involves promoting one of several task-sets in play into a most-active state. This process, often conceptualised as retrieving task parameters and stimulus-response (S-R) rules into procedural working memory, is a likely source of the reaction time cost of a task-switch, especially when no time is available for task preparation before the stimulus. We report two task-cuing experiments that asked whether the time consumed by task-set retrieval increases with the number of task-sets in play, whilst unconfounding the number of tasks with their frequency and recency of use. Participants were required to switch among 3 or 5 orthogonal classifications of perceptual attributes of an object (Experiment 1) or of phonological/semantic attributes of a word (Experiment 2), with a 100 or 1300 ms cue-stimulus interval. For two tasks for which recency and frequency were matched in the 3- and 5-task conditions, there was no effect of number of tasks on the switch cost. For the other tasks, there was a greater switch cost in the 5-task condition with little time for preparation, attributable to effects of frequency/recency. Thus retrieval time for active task-sets is not influenced by the number of alternatives per se (unlike several other kinds of memory retrieval) but is influenced by recency or frequency of use.The work described in this paper was carried out as part of a PhD project by FvtW under the supervision of SM and AL, supported by a studentship from the Economic and Social Research Council (UK)