Would you push someone into an oncoming train if doing so would save the lives of five others down the track? Or would you save the five people by flipping a switch that will kill one person down another track? In a study that combines philosophy and neuroscience, Princeton researchers used functional magnetic resonance imaging (fMRI) to analyze brain activity in people who were asked to ponder a range of such moral dilemmas. Co-authors of the paper are Jonathan Cohen and John Darley, both professors of psychology; Joshua Greene, Brian Sommerville, and Leigh Nystrom.

The results, published in Science (September 14, 2001), suggest that answers to such questions often do not grow out of a reasoned application of moral principles, as has been the long-held view. Instead, they draw on emotional reactions, particularly for certain moral dilemmas. In the study, eighteen people answered a battery of 60 personal and non-personal questions while undergoing MRI scanning. The scanning consistently showed a greater level of activation in emotion-related brain areas during the personal moral questions than during the impersonal moral or non-moral questions.

The researchers also measured how long it took subjects to respond to questions. In the few cases in which people said it is appropriate to take action in the personal moral questions -- like pushing a person off the footbridge -- they tended to take longer to make their decisions. This suggests that these individuals were working to overcome a primary emotional response, the researchers concluded.
Cohen notes that the current study "is a nice example of how cognitive neuroscience -- and neuroimaging in particular -- provide an interface between the sciences and the humanities."

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