Performance in sustained attention tasks is known to be slowed by the occurrence of unexpected task-irrelevant distractors (novelty distraction) and the detection of errors (posterror slowing), 2 wellestablished phenomena studied separately and regarded as reflecting distinct underpinning mechanisms. We measured novelty distraction and posterror slowing in an auditory-visual oddball task to test the hypothesis that they both involve an orienting response. Our results confirm that the 2 effects exhibit a positive interaction. We show that a trial-by-trial measure of surprise credibly accounts for our empirical data. We suggest that novelty distraction and posterror slowing both reflect an orienting response to unexpected events and a reappraisal of action plans.