Princeton University researchers say when humans make those tough choices, the balance of activity in areas of their brains responsible for emotion and logic shifts, depending on the scenario they face.
One researcher says the findings could offer insight into ways to balance emotion and reason in the days and weeks after the brutal terrorist attacks in New York and Washington, D.C.Graduate philosophy student Joshua Greene led a team examining two groups, each with nine people. Participants answered 60 questions while undergoing a functional magnetic resonance imaging (fMRI), which shows activity in regions of the brain.
The questions ranged from non-moral questions, such as which coupons to use at a store, to "non-personal" ethical dilemmas, such as whether to keep the money in someone else's lost wallet.
Then the volunteers were presented with personal ethical dilemmas. mirroring well-known moral-philosophical problems: If a runaway train is about to hit five people, is it ethical for a bystander to throw a switch to divert the train to another track, where it would hit one person? On the other hand, would it be ethical for someone standing on a footbridge above the track to push another bystander off the bridge onto the tracks in front of the train to stop it before it hits the five people?
Greene says in nearly every case, people will agree that the first choice is ethical, while the second is not. Curious as to why people respond differently since the result is the same in both situations, Greene speculated that the scenarios call on different psychological processes.
Greene and his colleagues found that personal moral questions generated more activity in areas of the brain believed to be involved in higher emotional processing, while impersonal moral dilemmas triggered less activity. Non-moral scenarios set off still less activity.
On the other hand, impersonal moral dilemmas and non-moral scenarios prompted more activity in areas of the brain responsible for simple problem solving and working memory.
Greene also found that participants who felt that taking action in the personal moral dilemmas was acceptable took longer to come to a decision. The researchers speculate they had to overcome an emotional barrier. "You have a kind of visceral, emotional reaction that pushes you away from saying, 'Yes, that's OK,'" Greene says.
Senior study author Dr. Jonathan Cohen, director of Princeton's Center for the Study of Brain, Mind and Behavior, says, "When we make our moral decisions, [people] are influenced not just by cold, calculating logic, but also by emotional considerations."
"Emotions play a very important, and, in some ways, tightly integrated role together with non-emotional processes in determining human behavior and human judgments," he says.
"The prospect of pushing this person off the bridge as they stare into your eyes, pleadingly, arouses all these emotions that you take account of when you make your decision about what's morally acceptable and what's not," says Cohen. "That doesn't mean it's right or wrong, it simply means that this is what people seem to do."
Robert Kane, a professor of philosophy at the University of Texas at Austin, says neuroscience research shows that reasoning is intertwined with emotions. "The emotional centers of the brain are tied to the higher reasoning functions in the neo-cortex. We can't do any reasoning in life independently of our emotional reactions," says Kane.
Cohen says emotions "may reflect the coding into human behavior of important principles that are rational when viewed at a higher level, such as a social level." He says the findings could have practical implications, for instance, by adding the sometimes erratic nature of human emotion to economic models to make them more accurate.
More immediately, he says the findings about the balance between emotion and reason may be relevant to how people should respond to an emotionally charged moral decision, such as Tuesday's attacks on the United States.
"On the one hand, there's this unavoidable sense that we all have that we want something to happen, and we want something to happen quick," says Cohen. "On the other hand, it's not clear that the best [reaction to] that emotion is to go ahead and start striking. There has to be some integration of that emotion with the rational process that figures out how to achieve the goal that the emotion wants."