March 6 2003 - Someone who says
"I'm of two minds about this" is not just procrastinating. Research conducted by Kip Smith,
using Positive Emission Tomography (a brain imaging technique), shows that the reason why people often can't make up their minds may be
due to the brain using different areas in the decision-making process.
"We're of at least two minds," Smith said. "This research shows the brain
is not a single entity. There is not a single executive decision-making mechanism there."
Smith's research produced neuroimages of the parts of the brain
used in different types of choices. Smith found evidence for two systems used to make decisions
in the brain: deliberative and emotional. Deliberative systems, also referred to as
calculation areas, utilize parts of the brain related to mathematics and rational
decisions. Emotional systems utilize older, more primal parts of the brain.
Smith considers that individual behavior is affected by attitudes about
payoffs, such as gains and losses, as well as beliefs about outcomes, such as risk
and ambiguity. During his experiments, participants' brain activities were measured
by positron emission tomography. The research demonstrated a relationship between
brain activity and observed choices. Smith's results allowed him to create images of
the parts of the brain used for risk, ambiguity, gains and losses with decision making
in the experiment.
Smith said some of the results were surprising. "We thought that risky
losses would be processed by the part of the brain that responds to fear, but they were
dealt with in a fairly rational manner," he said. Also, the deliberative areas of the
brain did not show high usage with decisions relating to risky gains. "It could be that
the emotional areas overwhelm the calculation areas. The results are correlational,
because it's not a completely controlled experiment."
Smith's results were published in the June 2002 issue of Management
Science in the article "Neuronal Substrates for Choice under Ambiguity, Risk, Gains and Losses."
The paper was co-authored by John Dickhaut, University of Minnesota; Kevin McCabe,
George Mason University; and Jose V. Pardo, Veterans Affairs Medical Center and the
University of Minnesota. A second paper, "The Impact of the Certainty Context on the
Process of Choice," is forthcoming in the Proceedings of the National Academy of
Sciences. Dickhaut, McCabe and Pardo, as well as Aldo Rustichini, University of
Minnesota, and Jennifer C. Nagode, Veterans Affairs Medical Center and the University
of Minnesota, co-authored the second paper.
Positive Emission Tomography
Positron Emission Tomography, or PET is a procedure designed to produces images of the
body's biological processes. Conventional imaging (x-rays, CT scans, etc) show the body's
anatomy whereas PET reveals the metabolic function of an organ or tissue.
Typically, a patient or experimental subject is given an intravenous injection of FDG, a glucose analog labeled with
radioactive fluorine and asked to lie still for 45-60 minutes while the isotope is
distributed throughout the body and absorbed by the cells. Then, the subject lies on a
table called a scanning bed and is moved slowly through a scanner which detects the
distribution of the injected tracer. The scanner can create a three-dimensional image of
the tracer's distribution when analyzed by a computer.