Bad Decisions Arise
from Faulty Information, Not Faulty Brain Circuits
Making
decisions involves a gradual accumulation of facts that support one choice or
another. A person choosing a college might weigh factors such as course
selection, institutional reputation and the quality of future job prospects.
But
if the wrong choice is made, Princeton University researchers have found that
it might be the information rather than the brain's decision-making process
that is to blame. The researchers report in the journal Science that erroneous
decisions tend to arise from errors, or "noise," in the information
coming into the brain rather than errors in how the brain accumulates
information.
Previous
measurements of brain neurons have indicated that brain functions are
inherently noisy. The Princeton research, however, separated sensory inputs
from the internal mental process to show that the former can be noisy while the
latter is remarkably reliable, said senior investigator Carlos Brody, a
Princeton associate professor of molecular biology and the Princeton
Neuroscience Institute (PNI), and a Howard Hughes Medical Institute
Investigator.
"To
our great surprise, the internal mental process was perfectly noiseless. All of
the imperfections came from noise in the sensory processes," Brody said.
Brody worked with first author Bingni Brunton, now a postdoctoral research
associate in the departments of biology and applied mathematics at the
University of Washington; and Matthew Botvinick, a Princeton associate
professor of psychology and PNI.
The
research subjects -- four college-age volunteers and 19 laboratory rats --
listened to streams of randomly timed clicks coming into both the left ear and
the right ear. After listening to a stream, the subjects had to choose the side
from which more clicks originated. The rats had been trained to turn their
noses in the direction from which more clicks originated.
The
test subjects mostly chose the correct side but occasionally made errors. By
comparing various patterns of clicks with the volunteers' responses,
researchers found that all of the errors arose when two clicks overlapped, and
not from any observable noise in the brain system that tallied the clicks. This
was true in experiment after experiment utilizing different click patterns, in
humans and rats.
The
researchers used the timing of the clicks and the decision-making behavior of
the test subjects to create computer models that can be used to indicate what
happens in the brain during decision-making. The models provide a clear window
into the brain during the "mulling over" period of decision-making,
the time when a person is accumulating information but has yet to choose, Brody
said.
"Before
we conducted this study, we did not have a way of looking at this process
without inserting electrodes into the brain," Brody said. "Now thanks
to our model, we have an estimation of what is going on at each moment in time
during the formation of the decision."
The
study suggests that information represented and processed in the brain's
neurons must be robust to noise, Brody said. "In other words, the 'neural
code' may have a mechanism for inherent error correction," he said.
"The
new work from the Brody lab is important for a few reasons," said Anne
Churchland, an assistant professor of biological sciences at Cold Spring Harbor
Laboratory who studies decision-making and was not involved in the study.
"First, the work was very innovative because the researchers were able to
study carefully controlled decision-making behavior in rodents. This is
surprising in that one might have guessed rodents were incapable of producing
stable, reliable decisions that are based on complex sensory stimuli.
"This
work exposed some unexpected features of why animals, including humans,
sometimes make incorrect decisions," Churchland said. "Specifically,
the researchers found that errors are mostly driven by the inability to
accurately encode sensory information. Alternative possibilities, which the
authors ruled out, included noise associated with holding the stimulus in mind,
or memory noise, and noise associated with a bias toward one alternative or the
other."
The
work was funded by the Howard Hughes Medical Institute, Princeton University
and National Institutes of Health training grants.
Story Source:
The
above story is reprinted from materials provided byPrinceton University. The original article was written by
Catherine Zandonella.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
1.
B. W. Brunton, M. M.
Botvinick, C. D. Brody. Rats and Humans Can Optimally Accumulate
Evidence for Decision-Making. Science, 2013; 340 (6128): 95
DOI:10.1126/science.1233912
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Princeton University (2013, April 15). Bad decisions arise from
faulty information, not faulty brain circuits. ScienceDaily.
Retrieved April 16, 2013, from http://www.sciencedaily.com/releases/2013/04/130415172429.htm
