Legal decision making involves assessing the defendant's responsibility for the crime and choosing an appropriate punishment. To determine the neural correlates of these processes, Buckholtz et al. have used functional MRI to scan volunteers who made legal decisions based on written scenarios. The level of activity in the right dorsolateral prefrontal cortex correlated with the level of responsibility that the volunteers assigned to the defendant, whereas activity in the amygdala, the medial prefrontal cortex and the posterior cingulate cortex predicted punishment magnitude, indicating that distinct neural systems underlie the two processes in legal decision making. Here is their abstract:
Legal decision-making in criminal contexts includes two essential functions performed by impartial “third parties:” assessing responsibility and determining an appropriate punishment. To explore the neural underpinnings of these processes, we scanned subjects with fMRI while they determined the appropriate punishment for crimes that varied in perpetrator responsibility and crime severity. Activity within regions linked to affective processing (amygdala, medial prefrontal and posterior cingulate cortex) predicted punishment magnitude for a range of criminal scenarios. By contrast, activity in right dorsolateral prefrontal cortex distinguished between scenarios on the basis of criminal responsibility, suggesting that it plays a key role in third-party punishment. The same prefrontal region has previously been shown to be involved in punishing unfair economic behavior in two-party interactions, raising the possibility that the cognitive processes supporting third-party legal decision-making and second-party economic norm enforcement may be supported by a common neural mechanism in human prefrontal cortex.