Studies have consistently found that the ERN amplitude is larger when subjects make fewer errors (Amodio, Jost, Master, & Yee, 2007; Amodio, Master, Yee, & Taylor, 2007; Gehring et al., 1993; Hajcak et al., 2003b). Infrequent errors might make error commission especially significant, thus altering the amplitude of error signaling. Differences in subjects’ performance may thus pose a confound when comparing ERP across groups with different error rates and reaction times (Hajcak, Vidal, & Simons, 2004; Yeung, 2004). That is, if a group of participants has larger ERNs than a control group, and commit fewer errors than the control group, it is possible that the between-group behavioral differences might account for variation in the ERN. However it is possible to control subjects’ performance by providing feedback throughout the task (e.g., Hajcak & Foti, in press) or by only comparing subjects who are matched on performance (e.g., Tsai, Young, Hsieh, & Lee, 2005).
