Monday, March 26, 2007

Damage to an area of the brain behind the forehead, inches behind the eyes, transforms the way people make moral judgments

Benedict Carey:

In a new study, people with this rare injury expressed increased willingness to kill or harm another person if doing so would save others’ lives.

The findings are the most direct evidence that humans’ native revulsion to hurting others relies on a part of neural anatomy, one that evolved before the higher brain regions responsible for analysis and planning.

The researchers emphasize that the study was small and that the moral decisions were hypothetical; the results cannot predict how people with or without brain injuries will act in real life-or-death situations. Yet the findings, appearing online yesterday, in the journal Nature, confirm the central role of the damaged region, the ventromedial prefrontal cortex, which is thought to give rise to social emotions, like compassion.

Previous studies showed that this region was active during moral decision making, and that damage to it and neighboring areas from severe dementia affected moral judgments. The new study seals the case by demonstrating that a very specific kind of emotion-based judgment is altered when the region is offline. In extreme circumstances, people with the injury will even endorse suffocating an infant if that would save more lives.

“I think it’s very convincing now that there are at least two systems working when we make moral judgments,” said Joshua Greene, a psychologist at Harvard who was not involved in the study. “There’s an emotional system that depends on this specific part of the brain, and another system that performs more utilitarian cost-benefit analyses which in these people is clearly intact.”

Morality, Psychopaths and Emotions

Is Morality a Result of Evolution? Study Shows Biological Roots of Moral Decisions

Posing the right question

Biologist sees human morality evolving from the sociality of primates

Primate origins of morality

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