Error-related pupil dilation is sensitive to the evaluation of different error types.

Adjusting behavior following errors is essential for successful goal-directed performance. Error-related pupil dilation indicates increased autonomic arousal and has been shown to predict adaptive adjustments of post-error behavior. Because different types of errors may require different behavioral adjustments, we investigated whether this process is also sensitive to the evaluation of different types of errors. We used a four-choice flanker task where errors occur either by pressing a button associated with the distractors (flanker errors), or by pressing a button not associated with the stimulus at all (nonflanker errors). Flanker errors imply suboptimal selective attention to the target and are therefore of increased significance for successful performance. Pupil dilation was larger for flanker errors than nonflanker errors, and only pupil dilation on flanker errors predicted a decrease of error probability on the next trial. Moreover, the error-related negativity, an electrophysiological marker of early error monitoring in the medial frontal cortex, was larger on flanker errors anticipating the effect of error type on pupil dilation. These results show that error-related pupil dilation is sensitive to the type and significance of errors and correlates with adaptive behavioral adjustments accordingly. This suggests that mechanisms underlying error-related pupil dilation receive inputs from error evaluation mechanisms in the medial frontal cortex.