Seeking to find the underpinnings of human moral judgment, scientists monitored brain activity in nine people who were presented with various hypothetical dilemmas. The investigators found that particular emotional centers in the brain charged up when the dilemmas involved people in clear and present danger. But the brain activity was diminished in moral decisions that did not involve ``up close and personal'' harm to others--such as deciding whether to keep money found in a lost wallet.

The findings are published in the September 14th issue of Science. Joshua D. Greene of Princeton University in New Jersey led the study.

According to Greene's team, a classic example of how puzzling moral judgment can be is the ``trolley dilemma.'' In this scenario, people have a choice of letting a runaway trolley kill five people, or to throw a switch that will divert the trolley to a set of tracks where it will kill one person. Most people, the researchers note, say that throwing the switch is the right choice.

Then there is the ``footbridge dilemma,'' in which you can save five people from that runaway trolley by pushing a stranger from an overpass into the trolley's path. To this, most people say no.

``How is it that nearly everyone manages to conclude that it is acceptable to sacrifice one life for five in the trolley dilemma but not in the footbridge dilemma...?'' the authors write.

Some argue that the footbridge scenario involves ``using'' another person's life as a means to an end--a morally objectionable option, Greene's team explains.

However, the report indicates, most people also say that throwing the switch is the right choice when the trolley dilemma has an added twist: the track on which the one person stands loops around to come back to the original five people. In this case, the authors argue, that one person is indeed ''used'' as an obstacle to stop the trolley from coming back around. Yet most people would still throw the switch.

The answer to this puzzle, the researchers suggest, may be that the footbridge dilemma engages people's emotions to a greater extent. And such emotional involvement changes the way we view morality.

And, according to the report, their experiments support that idea.

In situations where no moral question was at hand--such deciding whether to take a train or bus--certain emotion-linked brain areas showed no remarkable activity during brain scans. The results were similar when the moral question was more ''impersonal''--as in voting for a policy expected to cause more deaths than an alternative would.

In contrast, a scenario that, for example, involved stealing one person's organs to save the lives of five others, triggered increased activity in the brain's emotional centers.

``We argue that moral dilemmas vary systematically in the extent to which they engage emotional processing and that these variations in emotional engagement influence moral judgment,'' Greene and colleagues conclude.

But, they note, it is questionable whether this better understanding of how moral judgments are formed will affect how people view their own judgments.

SOURCE: Science 2001;293:2105-2108.

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