The United States National Institute of Mental Health has recently promoted the Research Domain Criteria framework, which emphasizes the study of neurocognitive constructs that cut across different disorders. These constructs are said to express dimensionally across the population, giving rise to psychopathologies only in the extreme cases where that expression is maladaptive. Inspired by the RDoC framework, we propose that recent insights into the function of anterior cingulate cortex (ACC), a brain area said to be responsible for selecting and motivating extended behaviors, may elucidate the etiology of a diverse array of mental disorders. We argue that ACC function contributes to individual differences in personality traits related to reward sensitivity and persistence, and propose that the maladaptive expression of these traits contributes to multiple mental and neurological disorders. Our discussion is organized around a computational framework that relates the reward processing and control functions of ACC, as revealed by two electrophysiological phenomena called the reward positivity and frontal midline theta oscillations, to a distributed neural system underlying cognitive control.