Mr Spock, the fictional Vulcan famously logical and lacking in emotion, sacrificed himself for his comrades in the movie Star Trek II: The Wrath of Khan with the following words to Captain Kirk: “The needs of the many outweigh the needs of the few, or the one ”

Now, revealing new research shows that people with damage to a key emotion-processing region of the brain also make moral decisions based on the greater good of the community, unclouded by concerns over harming an individual.

It is the first study to demonstrate how emotion impacts moral judgement and sheds light on why people often act out of respect for an individual rather than choosing to act in a more logical, utilitarian way. The findings could cause a rethink in how society determines a “moral good”, and challenge the 18th-century philosophies of Immanuel Kant and David Hume.

Antonio Damasio at the University of Southern California in Los Angeles, US, and colleagues recruited 30 people for their experiment. Six of the subjects had suffered damage to a region in the front of the brain known as the ventromedial prefrontal cortex (VMPC), which regulates emotions. The participants had this brain injury as a result of an aneurism or tumour growth in the VMPC region.


Twelve participants in the study had damage to other parts of the brain but not the VMPC. And the remaining 12 subjects had no brain injury whatsoever.

“Utilitarian” action

The researchers presented participants with various scenarios (scroll to the bottom for several examples) and asked them to make decisions based on the information provided. Some of the situations involved moral decision-making. For example, subjects had to say whether they would throw a person in front of a train if doing so would stop the train from barrelling into five workmen, killing all five.

In such a situation, most people would find it morally unacceptable to push someone to his or her death – even if doing so would save the lives of others. And this was the reaction of the healthy participants or those that had injury to brain regions excluding the VMPC. But people with damage to the VMPC showed a willingness to take this type of “utilitarian” action.

“You have one group that is ready to endorse what we would regard as an overly utilitarian judgment and the other far less” willing to do so, explains Damasio. He notes that the patients with VMPC damage generally made the same decisions as their control counterparts when it came to non-moral scenarios.

Subtle scenarios

Notably, people with VMPC damage were just as likely as their counterparts to endorse “impersonal” moral decisions that involved indirectly putting strangers at risk for the greater good. These impersonal moral scenarios involved, for example, encouraging the use of a vaccine that would protect the public but cause an adverse reaction in a few individuals.

These results suggest that emotions play a crucial role in moral decisions involving personal contact – but not in moral judgments involving distant, indirect impacts on other people. “What’s beautiful to me is how subtly different the situations are,” says Marc Hauser at Harvard University in Cambridge, Massachusetts, US, one of the researchers involved.

The finding that some moral judgments involve emotions while others do not supports the supposedly diametrically opposed thinking of philosophers Immanuel Kant and David Hume.

“It means both Kant and Hume are right. Philosophers will have a fit because they like to choose sides,” says Frans de Waal at Emory University in Atlanta, Georgia, US. Hume believed that people could be motivated to make proper moral decisions based on their sympathy for others. Kant, meanwhile, warned that moral judgments might be corrupted by emotions.

Personal dignity

Philip Kitcher, who teaches philosophy at Columbia University in New York, US, notes that the study of brain damaged individuals presents a unique challenge to Kant’s philosophy. While Kant cautioned against the corruptive influence of emotions, he also argued that individuals have personal dignity, which must be respected.

Yet in the new study, subjects who had impaired emotion processing due to VPMC damage showed the least concern for individual dignity in the personal moral dilemmas that involved directly harming another person to save others. This provides strong biological evidence that emotions enable us to respect individual dignity, says Kitcher.

“Emotions are an anchor for our moral systems. If you remove that anchor you can end up anywhere,” says de Waal.

Examples of scenarios used in the experiment:

Non-Moral Scenario: Investment Offer

You are at home one day when the mail arrives. You receive a letter from a reputable corporation that provides financial services. They have invited you to invest in a mutual fund, beginning with an initial investment of one thousand dollars.

As it happens, you are familiar with this particular mutual fund. It has not performed very well over the past few years, and, based on what you know, there is no reason to think that it will perform any better in the future.

Would you invest a thousand dollars in this mutual fund in order to make money?

Impersonal Moral Scenario: Standard Trolley

You are at the wheel of a runaway trolley quickly approaching a fork in the tracks. On the tracks extending to the left is a group of five railway workmen. On the tracks extending to the right is a single railway workman.

If you do nothing the trolley will proceed to the left, causing the deaths of the five workmen. The only way to avoid the deaths of these workmen is to hit a switch on your dashboard that will cause the trolley to proceed to the right, causing the death of the single workman.

Would you hit the switch in order to avoid the deaths of the five workmen?

Personal Moral Scenario: Submarine

You are the captain of a military submarine travelling underneath a large iceberg. An onboard explosion has caused you to lose most of your oxygen supply and has injured one of your crew who is quickly losing blood. The injured crew member is going to die from his wounds no matter what happens.

The remaining oxygen is not sufficient for the entire crew to make it to the surface. The only way to save the other crew members is to shoot dead the injured crew member so that there will be just enough oxygen for the rest of the crew to survive.

Would you kill the fatally injured crew member in order to save the lives of the remaining crew members?

Personal Moral Scenario: Infection

Someone you know has AIDS and plans to infect others, some of whom will die. Your only options are to let it happen or to kill the person.

Do you pull the trigger?

Journal reference: Nature (DOI: 10.1038/nature05631)