The ventromedial prefrontal cortex (VMPC) is located just behind the forehead and is a key emotion-processing region of the brain. Subjects with damage in this area were willing to sacrifice one life if it meant saving others’ lives. The VMPC is thought to be the area controlling social emotions like compassion to fellow human beings.

The study is a first of its kind to shed light on how emotions often cloud people's judgments. But the researchers were quick to point out the hypothetical nature of the study. How people would react in real and dramatic situations was unclear, they wrote in the journal Nature.

Previous studies have demonstrated the utility of the ventromedial prefrontal cortex in moral decision-making.  Damage to this area caused by degenerative diseases like dementia was found to affect moral judgments. This study documents the role played by the region in controlling emotions.

Researchers recruited 30 people for an experiment to determine the role of damaged brains in moral dilemmas. Six of the subjects had damaged VMPC caused by an aneurism or tumour growth in the area. Twelve participants had brain damage to areas other than the VMPC, while the remaining 12 had no brain damage at all.

People with damage to the ventromedial prefrontal cortex are outwardly similar to other normal people in that they are intelligent and lucid. However they appear detached from social subtleties and emotions that govern normal people.

The researchers gave a set f hypothetical scenarios to all subjects and assessed their responses.

One scenario asked the participants whether they in the guise of a military submarine captain would kill a crewmember to save the rest of them. The scenario outlined that oxygen supply was running out and the injured crewmember was going to succumb to his wounds.

Another situation asked the participants to decide whether to divert a runaway train that was about to kill a group of five workmen. If they were to divert the train to hit another man, these five workers would be saved, the question revealed.

The group with ventromedial injuries was twice as likely to make emotionless judgments like choosing to kill the injured crewmember and pushing someone in front of the train.

Lead author Dr. Michael Koenigs, currently a neuroscientist at the National Institutes of Health, said the difference was clear to see. Patients with ventromedial injuries were able to make moral judgments in high-conflict situations albeit of an imaginary nature.

Dr. Antonio Damasio, a co-author of the study and a neuroscientist at the University of Southern California said people with damage to VMPC were willing to make utilitarian judgments. “This area, when it’s working, will give rise to social emotions that we can feel, like embarrassment, guilt and compassion, that are critical to guiding our social behavior,” he added.

The researchers said the intent f the study was not to judge people, but rather to stress the importance of the ventromedial prefrontal cortex in emotional behavior. The VMPC has evolved over time to give man the trait of respecting individual dignity, they added.

"What's beautiful to me is how subtly different the situations are," said co-author Marc Hauser at Harvard University in Cambridge. "This shows a much more subtle, a much more nuanced view, which of course makes the whole problem, the science of morality, infinitely more interesting."