Neurologists have identified part of the brain that defines us as human and allows emotion and intuition to work in tandem with logic to solve moral dilemmas.

The brain section is crucial to solving extreme moral conundrums but rather than applying rational thinking alone, decisions are coloured by emotion, a study shows.

It is the first time that emotion has been demonstrated to play a part in making judgments between right and wrong and helps to explain why people are humane rather than wholly rational.

The study suggests that people’s brains have evolved biologically and culturally to require an element of compassion and to reject utilitarian, robotic decision-making and philosophy.

Researchers in the US showed that a frontal lobe in the brain, the ventromedial prefrontal cortex, (VMPC) plays a crucial role in decision-making.

Antonia Damasio, of the University of Southern California, said: “This component of the system is one among several that contribute to our wisdom and humanity.

“The findings indicate that purely rational accounts of moral judgments do not describe all the possible conditions humans face. Emotions appear to contribute to some of those judgments.

“It does appear from our study that humans reject extreme forms of utilitarian calculation. That rejection is tied to the deployment of social emotions.

“I think this mixed form of moral judgment, combining reason and emotion, manifests wisdom slowly accumulated over evolutionary time.”

The classic extreme moral dilemma is when people have to decide whether to kill one innocent person to save others. Rationally there is only the simple choice between the good of the one and the good of the many but most people waver or refuse to act for the apparent greater good.

The US study showed that rather than emotion entering the equation after choice has been made, it is an integral part of the decision-making process.

A group of 30 volunteers were asked to reach decisions on a range of moral dilemmas.

Six of the group had brain damage to the prefrontal cortex, leading them to lack empathy and compassion.

The results, published in the journal Nature, showed that they found it far easier to make an emotionless decision than any of the other volunteers. Those with damage stood out in their stated willingness to harm an individual, a prospect that usually generates “strong aversion”.

Scientists were, however, surprised to find that there was no difference in decisions on lower-grade moral judgments, such as whether to destroy a valuable statue to save someone’s life. Then, there was no difference between them and the other people in the study.

Professor Marc Hauser, of Harvard University, said: “Our work provides the first causal account of the role of emotions in moral judgments. What is absolutely astonishing about our results is how selective the deficit is.”

The researchers concluded: “These findings indicate that, for a selective set of moral dilemmas, the VMPC is critical for normal judgments of right and wrong. The findings support a necessary role for emotion in the generation of those judgments.”

Hard choices

Moral dilemmas that the volunteers had to consider:

— You, a man and a boy are the only survivors of a plane crash in the Himalayas. Your only chance of surviving is to walk for several days to find a village. The boy has a broken leg and virtually no chance of living. You have no food. The man suggests that you sacrifice the boy and eat his remains. Would you kill this boy so that you and the man may survive your journey to safety?

— Your ship sinks and you take to a lifeboat that is overcrowded and dangerously low in the water. Among your companions is an injured person who will not survive. The seas get rough and the boat will sink, drowning everyone, unless you throw the injured person overboard. Would you throw him out to save yourself and the others?

— You are among a group, including eight children, taken hostage in the jungle. The leaders of the terrorists offers to free you and the children if you kill a hostage to whom he has taken a dislike. Otherwise he says that he will kill all the hostages in the morning. Would you kill one of your fellow hostages in order to escape from the terrorists and save the lives of the eight children?

— It is wartime and an enemy doctor intends to perform fatal experiments on one of your children, but he will allow you to choose which it is. If you refuse he will experiment on both. Would you take one child to the lab to avoid having them both die?

— You set up camp on a sacred burial ground and your family must be put to death. The clan leader will let you go provided you kill your oldest son

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