Brain circuits to manage uncertainty
August 27th 2010 04:08
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(PhysOrg.com) -- Scientists at Harvard University have found that humans can make difficult moral decisions using the same brain circuits as those used in more mundane choices related to money and food.
These circuits, also found in other animals, put together two critical pieces of information: How good or bad are the things that might happen? What are the odds that they will happen, depending on one's choice? The results suggest that complex moral decisions need not rely on a specific "moral sense."
Amitai Shenhav and Joshua D. Greene of Harvard's Department of Psychology present the findings this week in the journal Neuron.
"It seems that our capacity for complex, life-and-death decisions depends on brain structures that originally evolved for making more basic, self-interested decisions about things like obtaining calories," says Shenhav, a doctoral student in psychology at Harvard. "Many of the brain regions we find to be active in major moral decisions have been shown to perform similar functions when people and animals make commonplace decisions about ordinary goods such as money and food."
Some researchers have argued that moral judgments are produced by a "moral faculty" in the brain, but Shenhav and Greene's work indicates that at least some moral decisions rely on general mechanisms also used by the brain in evaluating other kinds of choices.
"Research in neuroeconomics has identified distinct brain structures responsible for tracking the probability of various outcomes, the magnitude of various outcomes, and for integrating these two kinds of information into a decision," says Greene, an assistant professor of psychology at Harvard. "Our work shows that the parts of the brain people use for this last task -- combining assessments of outcome probability and magnitude into a final decision -- closely coincide with the brain regions we use daily when deciding how to spend money or choose foods."
Using real-time brain imaging, Shenhav and Greene presented 34 subjects with hypothetical choices between saving one life with certainty or saving several lives, but with no guarantee that this latter effort will succeed. The experiment systematically varied the number of lives at risk and the odds of success.
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