In other words, people with a rare injury - damage to the ventromedial prefrontal cortex - expressed increased willingness to kill or harm another person if doing so would save others’ lives. Benedict Carey's review (March 22 NY Times) of the paper by Koenigs et al. (PDF download HERE) notes that:
The findings are the most direct evidence that humans’ native revulsion to hurting others relies on a part of neural anatomy, one that evolved before the higher brain regions responsible for analysis and planning.Koenigs et al:
...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 emotions, 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). 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.
Lesions of the six VMPC patients displayed in mesial views and coronal slices. The colour bar indicates the number of overlapping lesions at each voxel. (Click on the figure to enlarge).