by Playfuls Staff |
22nd March 2007
Moral behavior can be seriously affected when a person suffers brain damage – so a study suggests.
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According to a new report, published in Nature, damage to the ventromedial prefrontal cortex (an area of the brain behind the forehead, inches behind the eyes) transforms the way a person makes moral decisions.
Sacrificing one human for the greater good of many is suddenly not a tricky choice anymore. Empathy, compassion, guilt, shame – all are diminished, while logical reasoning remains intact.
The study, funded by the National Institutes of Health, the National Science Foundation and private sources, was conducted by researchers from USC, the University of Iowa, Harvard University and Caltech.
The researchers worked with six people whose ventromedial prefrontal cortices were damaged by strokes or tumors, another 12 people without brain damage and an additional 12 others with damage in brain areas that regulate other emotions, such as fear.
Participants were given 50 hypothetical scenarios, with or without moral content. Then their answers were compared.
Researchers found no difference among groups in their responses to scenarios with no moral content. Then, there were similar responses to scenarios that did not require participants to directly kill or harm someone.
Members of all groups rejected decisions that would harm someone for the personal benefit of another, such as killing a newborn because a parent couldn't care for the infant.
When it came to making a decision about sacrificing one person for the greater good of others, people with damage to their ventromedial prefrontal cortex were about three times as likely to make it compared to people without brain damage or those with damage in a different part of their brains.
“Part of our moral behavior is grounded … in a specific part of our brains,” said Dr. Antonio Damasio, one of the study's lead authors and director of the Brain and Creativity Institute at USC.
The findings could not be used to predict actual behavior, Damasio said, because the scenarios presented in the study were unrealistic. More research is needed to determine if people with and without brain damage would react differently when faced with real-world dilemmas.
The New York Times said the study provides evidence that “human revulsion for hurting others” relies on neural anatomy. Experts said evidence of damage to this ventromedial area could sway judgments of moral competency in some court cases, the newspaper said.
Joshua D. Greene, a Harvard psychologist not involved in the research, said the study showed that moral judgment was shaped by two brain systems, one focused on intuitive emotional responses and another that controlled cognition. “When one of those systems is compromised, decisions are skewed,” he said.
Mirella Dapretto, associate professor of psychiatry at the UCLA Ahmanson-Lovelace Brain Mapping Center, said the brain might not work so simply. “One reason these people may have the guts to push someone off a bridge is that they don't comprehend how their actions would be evaluated by others,” she said.
“A nice way to think about it,” Dr. Damasio said, “is that we have this emotional system built in, and over the years culture has worked on it to make it even better.”
