Response-repetition costs reflect changes to the representation of an action.

Repeating a response from the previous trial typically leads to performance benefits. However, these benefits are eliminated, and usually reversed, when switching to a new task (i.e., response-repetition costs). Here, we test the proposal that response-repetition costs reflect changes in the representation of an action. To investigate this, we designed tasks that required participants to switch between color and shape judgments with experimentally induced outcomes. Critically, the stimuli and responses were constant across conditions; what differed was the number of outcomes associated with the responses. For both response time and error rate, response-repetition costs on task-switch trials were significantly reduced when response repetitions led to outcome repetitions relative to when response repetitions led to outcome switches. Moreover, response repetitions that led to outcome repetitions showed an advantage in response time (but not error rate) compared with when no outcomes were experimentally induced. We conclude that response-repetition costs reflect a change in the representation of an action and that action selection is largely grounded in the anticipation of the response-related outcomes.