In a another line of research, we have suggested that the anterior cingulate cortex (ACC) plays an evaluative function in cognitive control, by calculating an on-line index of the conflict between incompatible representations (i.e., crosstalk). This information is likely to be highly correlated with errors in performance, or may occur when responding is underdetermined. Consequently, ACC activity may serve as an index of an increased demand for cognitive control in particular task situations. We have shown that this theory can account for fMRI data on the relationship between ACC activity and error rate, as well as the increase in ACC activity that occurs when response conflict is increased (Carter, Braver, et al., 1998). Additionally, in simulation studies, we have shown how this theory can account for ACC findings in a variety of cognitive task domains (Botvinick, Braver, et al., 2001). More recent studies have focused on how the model can account for behavioral and imaging data in response inhibition and response selection paradigms (Jones et al., 2003).