The neural basis of implicit moral attitude--an IAT study using event-related fMRI

Recent models of morality have suggested the importance of affect-based automatic moral attitudes in moral reasoning. However, previous investigations of moral reasoning have frequently relied upon explicit measures that are susceptible to voluntary control. To investigate participant's automatic moral attitudes, we used a morality Implicit Association Test (IAT). Participants rated the legality of visually depicted legal and illegal behaviors of two different intensity levels (e.g., high intensity illegal = interpersonal violence; low intensity illegal = vandalism) both when the target concept (e.g., illegal) was behaviorally paired with an associated attribute (e.g., bad; congruent condition) or an unassociated attribute (e.g., good; incongruent condition). Behaviorally, an IAT effect was shown; RTs were faster in the congruent rather than incongruent conditions. At the neural level, implicit moral attitude, as indexed by increased BOLD response as a function of stimulus intensity, was associated with increased activation in the right amygdala and the ventromedial orbitofrontal cortex. In addition, performance on incongruent trials relative to congruent trials was associated with increased activity in the right ventrolateral prefrontal cortex (BA 47), left subgenual cingulate gyrus (BA 25), bilateral premotor cortex (BA 6) and the left caudate. The functional contributions of these regions in moral reasoning are discussed.