Public Release: 

Decision making isn't always as rational as you think (or hope)

Michigan State University

SAN FRANCISCO -- When making tough choices about terrorism, troop surges or crime, we usually go with our gut.

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 joins 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," today 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."


Contact: Jamie DePolo, Michigan Agricultural Experiment Station: (609) 354-8403,


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

For photos, links and full coverage of MSU at AAAS, see

NOTE: Joseph Arvai can be reached Feb. 15-19 at AAAS on his cell phone at (517) 944-1649. Jamie DePolo can be reached on her cell phone at (609) 354-8403.

The Michigan Agricultural Experiment Station is one of the largest research organizations at Michigan State University. Founded in 1888, the organization funds the work of nearly 400 scientists in five colleges at MSU to enhance agriculture, natural resources, and families and communities in Michigan.

Michigan State University, the nation's pioneer land-grant institution, has been advancing knowledge and transforming lives through innovative teaching, research and outreach for more than 150 years. MSU is known internationally as a major public university with global reach and extraordinary impact. Its 15 degree-granting colleges attract scholars worldwide who are interested in combining education with practical problem solving.

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