Emotion and Cognition in Moral Judgment: An fMRI Investigation
Consider the following moral dilemma. A trolley is heading down a set of tracks toward five people who will be killed if it proceeds on its present course. You can save these five people by diverting the trolley onto a different set of tracks, one that has only one person on it, but if you do this that person will be killed. Is it morally permissible to turn the trolley and thus prevent five deaths at the cost of one? Most people say yes. Now consider a slightly different dilemma. Once again, a trolley is heading down a set of tracks toward five people. You are on a footbridge over the tracks next to a large man. The only way you can save these five people is to push this man off the bridge and into the path of the trolley. Is that morally permissible? Most people say no.
These two cases create a puzzle for moral philosophers (at least for those who take moral intuitions at face value): What makes it okay to sacrifice one for the sake of five in the first case but not in the second case? But there is also a psychological puzzle here: How does everyone know (or "know") that it's okay to turn the trolley but not okay to push the man off the bridge? One hypothesis is that we have an implicit understanding of a complex set of shared moral principles from which we deduce our answers. According to this theory our responses are, in both cases, the results of "cool" reasoning. A different hypothesis appeals to common emotional response rather than shared principles. The thought of pushing someone to his death with one's bare hands is, we'll suppose, more emotionally salient than the thought of hitting a switch that will have similar consequences. Somehow, the action described in the second case sets off an emotional "moral alarm" in each of us. According to this theory, our shared dispositions to respond emotionally to some things and not others explains the consistency found in people's reactions to these two cases.
"Cool" reasoning and emotional response are associated with different parts of the brain. While our understanding of these psychological functions and their neural substrates is far from complete, we are in a position to use the above theories to generate predictions about the brain's activity and to test these predictions using fMRI (functional Magnetic Resonance Imaging). Such a study is being carried out by Joshua Greene (Graduate Student, Dept. of Philosophy) under the supervision of Jonathan Cohen (Director, CSBMB; Professor of Psychology) and with the help of Leigh Nystrom (Senior Technical Staff II, CSBMB) and John Darley (Professor of Psychology).
Contact:
Jonathan Cohen