British and German scientists believe they have identified a specific area of
the human brain which appears to be responsible for intelligence.
The research - published in Science magazine - found that a part of the brain
called the frontal lateral cortex was the only area where blood flow
increased when volunteers tackled complicated puzzles involving sequences of
symbols and letters.
Their findings seem to support the 1904 theory of psychologist Charles
Spearman, who argued that people used a particular part of the brain when
performing complex tasks.
Other theories contend that intelligent thinking requires various portions of
the brain working together like different parts of an engine.
The results suggest that "general intelligence" derives from a specific
The researchers, from the Medical Research Council's Cognition and Brain
Sciences Unit at Cambridge University and from Dusseldorf University, used
scanning techniques to assess the blood flow in subjects' brains when they
were performing the tests.
Science magazine also carries an article attacking the scientists' approach
to the subject. It argues that human intelligence cannot be defined in such a
The debate over the nature of intelligence has continued since Charles
Spearman set his mind to the problem early in the last century.
He proposed that the same bright people tended to do well at different tasks
because they employed a generally useful component of their brains which he
called the "g" factor.
However, many questions about the mystery of intelligence remain unanswered.
The research, led by John Duncan from the MRC, asked volunteers to carry out
a number of "high-g" and "low-g" tasks which involved identifying mismatched
symbols or sets of letters.
High-g tests were designed to employ a wider range of cognitive functions and
be more challenging than low-g tests.
While taking the tests, the volunteers' brains were scanned using a technique
called positron emission tomography.
The scientists found that high-g tasks did not require numerous regions
spread around the brain to be used together.
Instead, activity was concentrated in the lateral frontal cortex, in one or
both brain hemispheres.
The researchers wrote: "The results suggest that "general intelligence"
derives from a specific frontal system important in the control of diverse
forms of behaviour."
But they acknowledged that this apparent intelligence centre might itself be
divided into finer components.
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