Train of thought: moral dilemmas exercise our emotions.© PhotodiscIf five people are trapped on a railway track and a train is approaching, is it morally right to divert the train onto another track where there is only one person? Most people would say yes. Would it be right to push a person onto the track to prevent the train from hitting the other five? This time, most people would say no.
The different responses puzzle philosophers, because the principle - sacrifice one life to save five - is the same in both cases.
Magnetic resonance images now show that our brains process the two dilemmas in fundamentally different ways, using brain regions responsible for emotion only in the second situation1.
"We've known almost nothing about how the brain handles moral dilemmas," says psychologist Jonathan Cohen, who conducted the experiment with colleagues at Princeton University in New Jersey. "Now it appears that when people make moral decisions, emotional responses play as much of a role as logical analyses."
When study participants made moral decisions about situations that have a personal element, such as throwing people off a sinking lifeboat, activity soared in four parts of the brain involved in processing emotion. Meanwhile, it sank in three regions associated with working memory, which stores and processes information in the short term.
The reverse happened when subjects judged less personal moral dilemmas, such as keeping the money found in a lost wallet, or considered questions that were not moral issues, such as whether to travel by bus or train in a given situation.
"This is fascinating research, which brings emotion firmly into the process of reasoning itself," says Helen Haste, an expert on the psychology of morality at the University of Bath in England. Many researchers have regarded moral reasoning as a purely analytical process, and deemed emotion as "something that gets in the way of reason", she says.
Gut feeling
Psychologists have had many clues to the importance of emotion in moral decision-making, says Joshua Greene, who led the Princeton study. Most famous is the nineteenth-century Vermont railroad worker Phineas Gage. He was transformed from a well-respected, law-abiding citizen to a shiftless, quarrelsome drifter after an iron rod passed through his eye socket and out of the back of his head in an accident.
"Right after the accident he seemed fine - he could talk, and do mathematics," Greene says. "But his moral behaviour changed dramatically, even though his basic reasoning ability seemed intact." More recently, Greene says, a patient who suffered similar brain damage started making disastrous moral decisions in his personal life, even though he could analyse abstract moral dilemmas logically.
“We don't have to write off emotions as silly, murky, irrational responses”
Jonathan Cohen,
Princeton University
Perhaps the most crucial finding of the study, Greene says, was that people took significantly longer to conclude that it was appropriate to push a person in front of the train than to decide it was inappropriate. "The people who said it was appropriate had to fight their emotions, so they were more hesitant," he says. "This says that emotion isn't just incidental, but really exerts a force on people's judgements."
The study makes no judgement about what decisions are moral, Cohen emphasizes. "What we've done has nothing to do with what is morally right, we are just describing how people come to decisions," he says. "That doesn't mean they've come to the right decision."
At the same time, there could be good reasons to trust our gut responses, he suggests. "Emotions may well be important adaptations. We don't have to write them off as silly, murky, irrational responses."
Princeton University
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