Preparing a task is sufficient to generate a subsequent task-switch cost affecting task performance

This study investigated the nature of switch costs after trials on which the cued task had been either only prepared (cue-only trials) or both prepared and performed (completed trials). Previous studies have found that task-switch costs occur following cue-only trials, demonstrating that preparing – without performing – a task is sufficient to produce a subsequent switch cost. However, it is not clear whether switch costs after these different types of trial reflect an impact of task switching upon task preparation or task performance on the current trial. The present study examined this question using a double-registration procedure with both cue-only and completed trials. Participants responded to both task-cue and target stimuli. In cue responses, a cost of switching task cues (cue-switch cost) but not of switching tasks (task-switch cost) followed both cue-only and completed trials. In target responses, a task-switch cost but no cue-switch cost followed both cue-only trials and completed trials, and this task-switch cost was larger following completed than cue-only trials. The presence of the task-switch cost in target responses following cue-only trials indicates a specific impact of previous preparation upon task performance, and the increased size of this cost following completed trials indicates an additional impact of previous performance. Together, these results suggest that both task preparation and task performance contribute to the subsequent task-switch cost affecting task performance.