The human brain is set up to simultaneously process two kinds of information: the emotional and the empirical. But in most people, emotional responses are much stronger than the rational response and usually take over, according to Michigan State University environmental science and policy researcher Joseph Arvai.

"People tend to have a hard time evaluating numbers, even when the numbers are clear and right in front of them," Arvai said. "In contrast, the emotional responses that are conjured up by problems like terrorism and crime are so strong that most people don't factor in the empirical evidence when making decisions."

Arvai joined four other scientists to discuss how people make decisions and evaluate risk at a symposium, titled "Numbers and Nerves: Affect and Meaning in Risk Information," at the American Association for the Advancement of Science annual meeting.

In his research, Arvai and graduate student Robyn Wilson, of Ohio State University, asked individuals to consider two risk scenarios common in many state parks. One involved crime -- vandalism and purse snatching -- and the other involved damage to property from white-tailed deer, such as auto-deer collisions. The participants were asked to indicate which problem required more attention from risk managers.

"The neat thing with crime and deer overpopulation is that both risks could be measured on the same scale, which made our jobs as researchers easier," Arvai explained. "But because crime incites such a negative emotional response from most people, it consistently received more attention, even when the numbers showed that the risks from deer were much worse. We had to ratchet up the deer damage until it was ridiculously high before people noticed that it was a higher risk than crime.

"The bigger problem we've uncovered is that this response isn't limited to crime and deer," he continued. "We see it happening in other areas: terrorism, the war in Iraq and infectious diseases."

Can this heart over head thinking be reversed?

"People can be given tools that help them to 'listen' more to the empirical side of their brains," Arvai said. "But in our experiments, the effects of these tools tend to be relatively short term. We've been able to make people aware that they're letting their emotions guide them, and we've developed decision aids that help them strike a better balance between their emotions and the numbers. But people tend to revert to decisions guided by emotions once the experiment is over, and they leave the room."

Arvai's research is funded by the National Science Foundation, NASA, the Michigan Agricultural Experiment Station and Ohio State University.

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