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Morality and the Brain: Is Choosing the Greater Good Rational or Just Cold?

For release: Thursday, May 10, 2007

You are adrift at sea in a lifeboat weighed down with too many people, including a wounded man who is near death.  Do you throw him overboard?

Throughout history, philosophers have debated these kinds of moral dilemmas.  Now, neuroscientists are joining the discussion, but instead of asking how we should make moral choices, they're asking how our brains actually make such choices.

Two recent studies suggest that when our ability to process emotions is impaired, our brains are more likely to shift toward utilitarian judgments.  In other words, we're likely to sacrifice the good of one for the good of many, tossing the fellow castaway into the sea. 

In a study published in Nature,* researchers probed the moral reasoning of people with damage to the ventromedial prefrontal cortex (VMPC), an area of the brain known to process emotions.  People with damage to the VMPC are known to undergo striking personality changes – including a diminished capacity for compassion, shame and guilt – that can destroy their relationships at work and at home.

The researchers presented a series of "impersonal" and "personal," emotionally-charged dilemmas to six people with VMPC damage and to several control subjects.  In one of the "impersonal" dilemmas, subjects were asked to imagine they were driving a runaway train hurtling toward five workmen.  Would they flip a switch so that the train veered toward a single workman on a different track?  Most subjects, whether or not they had VMPC damage, said yes.

But when presented with "personal" dilemmas – such as choosing whether or not to throw a lone workman in front of the trolley to save five – the subjects with VMPC damage were more likely to say they would sacrifice the solitary workman.

The study shows there are two systems in the brain that guide moral decision-making, says Michael Koenigs, Ph.D., a post-doctoral fellow at the National Institute of Neurological Disorders and Stroke (NINDS).

"One is a more conscious, rational system.  The other is a more emotional, intuitive system.  For high-conflict, debatable dilemmas, it seems like the emotional system plays a larger role in guiding behavior," says Koenigs, who contributed to the study as a graduate student at the University of Iowa in Iowa City.  The study was supported in part by a grant from NINDS to Antonio Damasio, M.D., Ph.D., who holds joint appointments in neurology at the University of Iowa and the University of Southern California in Los Angeles.

Another study, published in Sleep,** suggests that a lack of sleep also reduces the influence of emotion on morality, again causing a shift toward utilitarian judgments.  There, scientists at the Walter Reed Army Research Institute in Silver Spring, Maryland asked a group of soldiers to consider a set of moral dilemmas similar to those in the Nature study.  The soldiers were tested on half of the dilemmas after eight hours of sleep, and then tested on the other half after 53 hours without sleep.

When faced with a personal dilemma, some of the sleep-deprived soldiers were more likely to make the utilitarian choice (again, think of throwing one person in front of a train to save many) – but it depended on their level of emotional intelligence (EQ).  When they were tired, soldiers with low EQ tended to make more utilitarian choices.  In contrast, sleep deprivation did not affect the number of utilitarian choices made by soldiers with high EQ.

The authors suggest that perhaps EQ should be a factor in selecting people for military and civilian jobs (such as firefighting) that combine tough moral decisions with long waking hours.

One might wonder if differences in qualities like EQ affected the work of renowned moral philosophers.  Were the brains of utilitarian thinkers like Jeremy Bentham wired differently than those of Emil Kant and his followers, who prized respect for individuals?

"The [VMPC] might be a place to look," says Koenigs.

*Koenigs M, Young L, Adolphs R, Tranel D, Cushman F, Hauser M, Damasio A.  "Damage to the Prefrontal Cortex Increases Utilitarian Judgments."  Nature, April 19, 2007, Vol. 446(7138), pp. 908-911.

**Killgore WDS, Killgore DB, Day LM, Li C, Kamimori G, Balkin M.  "The Effects of 53 Hours of Sleep Deprivation on Moral Judgment."  Sleep, March 1, 2007, Vol. 30(3), pp. 345-352.

-By Daniel Stimson, Ph.D.

Last Modified May 11, 2007