December 9, 2005

Uncertainty Activates Brain’s Emotion Centers

Feelings take center stage when outcomes are unclear, imaging study reveals

Investing money, getting married, switching jobs: All big decisions tinged with uncertainty, loaded with risk.

Now, a new brain-imaging study finds that the higher the level of uncertainty, the more likely it is that emotion, not logic, will guide those choices.

That may not always be such a bad idea, though, since "emotions have information in them, too," according to study author Colin Camerer, the Axline professor of business economics at the California Institute of Technology.

"In these ambiguous situations, the emotions are saying, 'Let's be afraid, let's be on our guard,'" he said. "Then it's up to the brain's cortex, the intellectual center, to decide whether that's a true danger, or whether it's something you want to override."

Research by Camerer and his colleagues is helping turn old economic and behavioral theories of decision-making -- that they are guided by dry logic alone -- on their head.

Reporting in the Dec. 9 issue of Science, the Cal Tech team used real-time functional MRI to observe the brain activity of healthy adults as they engaged in card games or quizzes conducted under two conditions.

In one condition, players were asked to take a risk, but their odds were clear -- for example, they could win $10 by picking a red card from a deck of 20 cards, where they knew 10 of the cards were red and 10 were blue.

In the other condition, the risk was less clear -- participants hoped to draw a red card from a deck of 20 red and blue cards, but they were not told how many of the cards were red and how many were blue.

The second deck was just as likely to have more than 10 red cards as it was to have less, so the actual risk was the same as the first, "known" deck.

Nevertheless, previous research has shown that people will tend to avoid picking from the deck they know less about -- a behavior psychologists call "ambiguity aversion."

"Real-life" ambiguous situations like these crop up all the time, Camerer said.

"For example, you're traveling in a foreign country and you don't know what to order on a menu, or you're a venture capitalist trying to figure out whether nanotechnology will be a billion-dollar business in 10 years' time," Camerer said. "In these situations, it's really hard to pin down the possibilities."

Prior economic theory held that people simply used their intellect to estimate the most likely outcome, then made their decisions accordingly.

But the Cal Tech brain-scanning experiments suggest that's not always so.

To be sure, when players understood the risk of picking either a red or black card, their brain's "logic" centers -- located in the frontal lobes -- dominated.

But when participants felt they lacked information and were faced with uncertainty, emotional centers -- the primitive amygdala and the orbitofrontal cortex -- kicked into high gear.

"It's in the cases where you just don't know the odds that the amygdala is more persistent," Camerer said. In these situations, the amygdala appears to interact with the brain's frontal cortex via an emotions-linked intermediary, the orbitofrontal cortex.

"It's a kind of back-and-forth between emotion and cognition," Camerer said.

Dr. Paul Sanberg is director of the Center for Excellence for Aging and Brain Repair at the University of South Florida College of Medicine. "This is one of the few imaging studies that coincides with the theory that the emotions are much more involved in our decision-making processes, even straight economics and mathematical issues," he said.

In fact, according to Sanberg, the brain may view ambiguity with hostility -- not surprising, since the amygdala is closely linked with anger and aggression.

"The fact that the situation is more ambiguous and will have a more emotional component turns it into an 'enemy,'" he speculated.

Camerer said another circuit, the "reward-centered" striatal system, also swung into activity during moments of uncertainty. "We think that this system is recognizing -- probably from input from the emotional and cortical systems -- that 'these bets are where we know the odds are better, we're more sure of getting money,'" he explained.

Both he and Sanberg stressed that people use their brains in widely varying ways, so there's no hard and fast rule that explains all decision-making. "Some people are more emotional or less emotional," Sanberg said. "But all of these components will be in use when they are activated in these parts of the brain."

Still, some traditional economists may have trouble incorporating the emotions into theories governing corporate decision-making. But Camerer believes "feelings" can be extremely valuable guides when information is either muddled or scarce.

"The line people most often use is 'feel your emotions, but don't believe them,' " he said. "In other words, sometimes there really is useful information there, and it may trigger you to think more carefully about the situation -- if this person makes me nervous, just why is that?"

More information

For more on fMRI brain imaging, visit the Radiological Society of North America (www.radiologyinfo.org ).