Damage to the prefrontal cortex increases utilitarian moral judgements

Abstract

Is moral reasoning a predominantly rational process, or does emotion play its part? Tests performed by six patients with lesions in an area of the brain involved in the normal generation of emotions (the ventromedial prefrontal cortex) point to a specific and causal role for the emotions in moral judgements. These patients produced an abnormally 'utilitarian' pattern of judgements on certain types of moral dilemmas, those that we might classify as “gut wrenching”, such as having to decide whether to sacrifice one's child in order to save a number of other people. Their judgements were normal on other classes of moral dilemmas. As well as illuminating the normal role of emotions in moral judgement, this work has a bearing on the mechanisms behind the pathological moral behaviour found in people like psychopaths. Moral reasoning is thought of as being a mostly rational process. But it is shown that patients with lesions in an area of the brain necessary for the normal general emotions produce an abnormally 'utilitarian' pattern of judgments on certain types of moral dilemmas. The findings support an essential role for emotion in the generation of certain types of judgments. The psychological and neurobiological processes underlying moral judgement have been the focus of many recent empirical studies1,2,3,4,5,6,7,8,9,10,11. Of central interest is whether emotions play a causal role in moral judgement, and, in parallel, how emotion-related areas of the brain contribute to moral judgement. Here we show that six patients with focal bilateral damage to the ventromedial prefrontal cortex (VMPC), a brain region necessary for the normal generation of emotions and, in particular, social emotions12,13,14, produce an abnormally ‘utilitarian’ pattern of judgements on moral dilemmas that pit compelling considerations of aggregate welfare against highly emotionally aversive behaviours (for example, having to sacrifice one person’s life to save a number of other lives)7,8. In contrast, the VMPC patients’ judgements were normal in other classes of moral dilemmas. These findings indicate that, for a selective set of moral dilemmas, the VMPC is critical for normal judgements of right and wrong. The findings support a necessary role for emotion in the generation of those judgements.