We compared individual differences in the ERP associated with incorrect responses in a discrimination task with other ERP components associated with attentional control and stimulus discrimination (N2, P3. CNV). Trials with errors that are detected by the subject normally produce a negativity (N-E) immediately following the response followed by a positivity (P-E). The morphology of the N-E and the P-E is similar to that of the standard N2-P3 complex on correct discrimination trials. Our findings suggest that the P-E is a P3 response to the internal detection of errors. The N-E, however, appears to be distinct from the N2. Finally, even though both the contingent negative variation (CNV) and the N-E are associated with prefrontal cortex and the allocation of attention to response accuracy, the N-E and CNV did not relate to one another. (C) 2001 Elsevier Science B.V. All rights reserved.