First, we have the switch dilemma: A runaway trolley is hurtling down the 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.”
Then we have the footbridge dilemma: Once again, the trolley is headed for five people. You are standing next to a large man on a footbridge spanning the tracks. The only way to save the five people is to push this man off the footbridge and into the path of the trolley. Is that morally permissible? Most people say “No.”
Consider the crying baby dilemma: It’s war time, and you are hiding in a basement with several other people. The enemy soldiers are outside. Your baby starts to cry loudly, and if nothing is done the soldiers will find you and kill you, your baby, and everyone else in the basement. The only way to prevent this from happening is to cover your baby’s mouth, but if you do this the baby will smother to death. Is it morally permissible to do this?
Joshua D. Greene
http://www.wjh.harvard.edu/~jgreene/
Moral Dilemmas and the “Trolley Problem”
My main line of experimental research began as an attempt to understand the “Trolley Problem,” which was originally posed by the philosophers Philippa Foot and Judith Jarvis Thomson.
First, we have the switch dilemma: A runaway trolley is hurtling down the 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.”
Then we have the footbridge dilemma: Once again, the trolley is headed for five people. You are standing next to a large man on a footbridge spanning the tracks. The only way to save the five people is to push this man off the footbridge and into the path of the trolley. Is that morally permissible? Most people say “No.”
These two cases create a puzzle for moral philosophers: What makes it okay to sacrifice one person to save five others in the switch case but not in the footbridge case? 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 footbridge?
According to my dual-process theory of moral judgment, our differing responses to these two dilemmas reflect the operations of at least two distinct psychological/neural systems. On the one hand, there is a system that tends to think about both of these problems in utilitarian terms: Better to save as many lives as possible. The operations of this system are more controlled, perhaps more reasoned, and tend to be relatively unemotional. This system appears to depend on the dorsolateral prefrontal cortex, a part of the brain associated with “cognitive control” and reasoning.
On the other hand, there is a different neural system that responds very differently to these two dilemmas. This system typically responds with a relatively strong, negative emotional response to the action in the footbridge dilemma, but not to the action in the switch dilemma. When this more emotional system is engaged, its responses tend to dominate people’s judgments, explaining why people tend to make utilitarian judgments in response to the switch dilemma, but not in response to the footbridge dilemma.
If you make the utilitarian judgment sufficiently attractive, you can elicit a prolonged competition between these two systems. Consider the crying baby dilemma: It’s war time, and you are hiding in a basement with several other people. The enemy soldiers are outside. Your baby starts to cry loudly, and if nothing is done the soldiers will find you and kill you, your baby, and everyone else in the basement. The only way to prevent this from happening is to cover your baby’s mouth, but if you do this the baby will smother to death. Is it morally permissible to do this?
According to the dual-process theory, this dilemma is difficult because it, like the footbridge dilemma elicits a strong negative emotional response (“Don’t kill the baby!”), while at the same time eliciting a comparably compelling utilitarian response from the other system (“But if you don’t kill the baby, everyone dies.”) Difficult dilemmas like this one tend to elicit increased activity in the anterior cingulate cortex, a brain region associated with “response conflict.” And when people make utilitarian judgments in response to these difficult dilemmas, they exhibit increased activity in anterior regions of the dorsolateral prefrontal cortex.
Emotion, Reason, and the Gap Between Us and Them
by Joshua Greene
Moral Tribes: Emotion, reason, and the gap between us and them
KPCCRadio
http://www.youtube.com/watch?v=xbA1t8YkY2I
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