Effects of proactive control and reward incentives on the inhibition of sequentially linked motor actions.

Effects of proactive control on response inhibition have previously been studied using tasks such as the stop signal task in which participants are required to inhibit a single, isolated motor response. However, skilled, coordinated behavior often involves the execution of learned sequences of motor actions in which each action triggers the next with a degree of automaticity. Across three experiments, we investigated the effects of proactive control and reward incentives on the frequency of errors in a motor sequence learning task that requires inhibition of sequentially triggered motor actions. We observed graded effects of proactive control on inhibition success. Although cues indicating an upcoming stop trial led to a marked reduction in the frequency of slips-of-action, errors continued to occur despite significant cue-induced proactive slowing. When cues were combined with incentives for successful stopping, proactive control increased further, with an additional reduction in frequency of slips-of-action. These findings show that the effectiveness of proactive control in suppressing automatically triggered actions within learned sequences is jointly determined by the depth of proactive slowing and the motivational context.