From: xgl (
Date: Thu Jun 22 2000 - 16:58:52 MDT


     Contact: Teresa Thomas
     Carnegie Mellon University

     Carnegie Mellon brain scientists find human brain applies law of
least effort when solving problems

     PITTSBURGH -- Using brain imaging, scientists at Carnegie Mellon
University have discovered how the human brain goes to work on solving a
problem and how it employs surprising economies of effort in the

     The results, compiled by Psychology post-doctoral research
associate Erik Reichle and Professors Patricia Carpenter and Marcel
Just, all of Carnegie Mellon's Center for Cognitive Brain Imaging
(, appear in the June issue of Cognitive

     The Carnegie Mellon scientists found that the law of least effort
may apply to the brain. Their results indicate that partially separate
networks within the human brain support language and visual-spatial
processing. The Carnegie Mellon findings also suggest that our brains
may seek to minimize the mental workload by choosing the strategy that
makes less work for the brain.

     By studying thinking in a simple task that lends itself to either
a visual or a verbal solution, the researchers were able to identify
which of two strategies was being used. The findings are based on
functional magnetic resonance imaging (fMRI) scans showing that brain
function associated with a verbal strategy produced relatively more
activation in a network of brain areas specialized for language
processing, prominently including Broca's area, which governs the
ability to talk. The use of a visual strategy shifted the activation
towards a network of brain areas that process visual and spatial
information, particularly the parietal cortex.

     "The new findings demonstrate that different ways of thinking
engage different networks of brain areas, resulting in identifiable
brain activation patterns in each individual," Just said. "We can't
quite read a person's mind by watching their brain at work, but we can
reliably tell which way a person is thinking about a problem."

     The study measured brain activity in college students as they read
sentences such as "The star is not above the plus (sign)" and judged
whether the sentences were true or false of an accompanying simple
picture. The student participants were instructed on the use of both a
verbal and a visual strategy, and told when to use each one. Comparing
the meaning of a sentence to the content of a picture involves both
verbal and spatial thinking, and the comparison of their meaning can be
done in either a verbal or a spatial domain of thought.

     The Carnegie Mellon team also was surprised that the amount of
brain activation occurring with each strategy depended on how skilled
the participant was in that kind of thinking. Carpenter explained that
more skill was associated with less activation, just as more skill at
something physical like swimming results in less muscle activity to
perform a given task.

     "Individuals with better verbal skills had less activation in
Broca's area when they used the verbal strategy. Similarly, individuals
with better visual-spatial skills had less activation in the left
parietal cortex when they used the visual-spatial strategy," she added.

     These findings tie in with one of the Center for Cognitive Brain
Imaging's main goals of using brain imaging to determine not only which
parts of the brain are used for this or that task, but to also discover
the mental economics that dictate how the organization of brain areas
ends up dealing with a particular thinking task.

     "In the final analysis the brain is a biological system that does
its job by consuming biological resources and providing a service,
namely thinking or information processing," Just said. "But when there
is a choice of how to provide the service, mental economics may come
into play, with the brain using the method that is less costly for that
individual, namely the one in which he or she is more efficient."

     The researchers noted that this finding provides a possible
meeting ground between the brain and the mind -- relating the dynamics
of higher level thinking (in this case understanding of sentences and
pictures) and the dynamics of brain-level activity (how the brain
accomplishes the translation between the two domains of understanding).

     Because not all brains are alike in their efficiency at a given
task, one of the new directions these results may lead to is in
evaluating which method, verbal or visual, may be more effective for
instruction or communication for a given individual. The new results
show that choice is more than just a matter of taste; it is a matter of
mental efficiency.

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