Fundamentals of Risk

Looking for the roots of chancy behavior
August 1, 2006
An extreme skier

Is risk-taking unique to humans? Neurobiologist Michael Platt doesn't think so. He has studied the way monkeys make bets with a currency they happen to love: fruit juice. Two adult male rhesus macaques were trained to look at different targets and receive juice. Looking at one target produced a small amount every time. Looking at a different target produced smaller or larger amounts sporadically.

"The monkeys overwhelmingly preferred the risky option," concludes Platt, an assistant professor of neurobiology. "The riskier we made it, the more likely the monkeys were to choose it." It appeared that the monkeys really liked the large payouts of juice, even when they were getting less juice over the long haul. Electrodes in the reward centers of the monkeys' brains showed that neuron activity was higher when the monkeys made the riskier choices.

Do human brains reflect a similar attraction to risk? With the aid of a functional magnetic resonance imaging scanner (fMRI), researcher Scott Huettel and his colleagues at the Duke-UNC Brain Imaging and Analysis Center have been putting human subjects through decision-making drills to find out what happens in the brain when a person is confronted with a risky, certain, or ambiguous choice. The study, published in the March issue of the journal Neuron, shows that different regions of the brain control different types of decision making, which may help in the treatment of certain pathologies such as addictions and other compulsive behavior.

Huettel then wanted to see what would happen when subjects played poker, an activity known to attract people who exhibit addictive behavior. "We want to understand how people behave, what are the strategies people take," says Huettel, who is an assistant professor of psychiatry, neurobiology, and psychology. "It's not just the money element. One thing we're interested in is the idea of bluffing." Needless to say, boiling down a complex game to something that can be measured in the lab has not been easy.

Huettel found that his subjects, when they faced off against a computer, bluffed at all the right times--that is, when a hand was really bad. That was not the case when they knew they were playing another human. "When they bluff against a person, they seem to be afraid the person will catch them in the bluff."

The studies by Platt and Huettul are part of a new field called neuroeconomics, which attempts to understand decision making right down to the level of neurons. "This field has really exploded," says Platt. The pair co-direct the Center for Neuroeconomic Studies, established in 2005, and will continue to peer into the origins of decision making by animals--and humans.