According to the early mismatch theory, the ERN represents the detection of a mismatch between the representations of the actual and intended response (Bernstein et al., 1995; Coles et al., 2001; Falkenstein et al., 1991). Thus, ERN amplitude should be directly related to the degree of mismatch between the correct and actual response. Indeed, studies confirm that subjects have larger ERNs when the error response and the correct response are more dissimilar (Bernstein et al., 1995; Falkenstein, Hohnsbein, & Hoormann, 1995; Scheffers et al., 1996). This mismatch should also be larger when subjects are more certain of their errors. In fact, studies have shown that the ERN amplitude is increased when subjects are sure that they made an error, regardless of whether or not they actually make a mistake (Scheffers & Coles, 2000).
