How large the sin? A study of the event related potentials elicited by errors of varying magnitude.

We report the results of an experiment designed to elucidate the extent to which the error related ERP components are affected by response and stimulus similarity. We examined the ERPs under varying degrees of mismatch between the representations of actual and appropriate responses. We replicated the design used in an earlier study, which demonstrated that response similarity rather than stimulus similarity affected the amplitude of the error related negativity (ERN). We report the results of a spatial-temporal principal component analysis (PCA), which indicates that response similarity affects the amplitudes of the ERN and the fronto-central positive component, but not those of the P300 and the frontal negativity. The results provide evidence to suggest that the ERN and the proceeding positive deflection are error related and are sensitive to the degree of the committed error, whereas the P300 and the frontal negativity are not.