| Scientists Detect Two Decision-making Pathways in Human Brain
In a classic Aesop fable, the Ant diligently stores food for the
upcoming winter, while the Grasshopper lounges in the summer sun
oblivious to the impending change of season. Like the characters
in this tale, people are often torn between impulsively choosing
immediate rewards or more deliberatively planning for the future.
And now new research supported in part by the National Institute
on Aging (NIA), a part of the National Institutes of Health (NIH),
suggests why: human decision-making is influenced by the interactions
of two distinct systems in the brain which like the Ant and Grasshopper
are often at odds.
The finding, published in the October 15, 2004, issue of Science
has broad implications for predicting economic and behavioral health
patterns, says Richard Suzman, Ph.D., Associate Director of the
NIA's Behavioral and Social Research Program.
"This landmark study has the potential to reshape what we
should look at as we try to understand how people make both health
and economic decisions," Dr. Suzman says. "Since many
health and economic decisions involve choosing between short term
gratification and long term delays of rewards, this approach and
its finding are likely to have a significant impact on our ability
to influence health and economic behaviors such as diet, exercise,
and saving for retirement."
For the study, a research team which included NIA grantee David
Laibson, Ph.D., of Harvard University and the National Bureau of
Economic Research in Cambridge, MA, asked 14 participants to choose
between receiving money at an earlier or later date. For instance,
a participant might be asked to choose between receiving $27.10
today versus $31.25 in a month; or $27.10 in two weeks versus $31.25
in six weeks. As the participants made these choices, their brains
were scanned using functional magnetic resonance imaging (fMRI).
This imaging tool enables researchers to measure second-by-second
brain function in thousands of specific brain regions.
When participants chose between incentives that included an immediate
reward, fMRI scans indicated heightened activity in parts of the
brain, such as the limbic system, that are associated with emotional
decision making. In contrast, deliberative and analytic regions
of the brain, such as the prefrontal and parietal cortex, were activated
by all decisions, even those that did not involve an immediate reward.
However, when participants resisted immediate rewards and instead
chose delayed rewards, activity was particularly strong in these
deliberative areas of the brain.
"Our research suggests that consumers have competing economic
value systems. Our emotional brain has a hard time imaging the future,
even though our logical brain clearly sees the future consequences
of our current actions," Dr. Laibson says. "Our emotion
brain wants to max out the credit card, even though our logical
brain knows we should save for retirement."
Or, as the authors conclude, "The idiosyncrasies of human
preferences seem to reflect a competition between the impetuous
limbic grasshopper and the provident ant within each of us."
Editors: Richard Suzman, Ph.D., Associate Director of the
NIA's Behavioral and Social Research Program, is available
to comment on this study. To arrange an interview, contact Doug
Dollemore, (301) 496-1752; email@example.com