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 IQ
Found to be Hereditary
November 6, 2001 7:00 CDT
A new genetic study of
twins shows that a certain degree of intelligence is
genetically predetermined before birth. It indicates
that the ability to do well in intelligence tests is
linked with the amount of grey matter in the brain,
which largely depends on genes.
Scientists compared 20 sets of twins, half of whom were
identical and half fraternal. Their brains were examined
with a medical scanner that can distinguish between
grey matter and white matter. Grey matter, which appears
grey to the naked eye, refers to the areas of the brain
mainly composed of the heads of nerve cells. White matter
refers to the parts of the brain and spinal cord responsible
for communication between the various grey matter regions
and between the grey matter and the rest of the body.
The
researchers found that identical twins, who share the
same genes, had virtually the same amount of grey matter.
This was not the case in non-identical twins, who share
only half their genes. The researchers concluded that
genetic factors are responsible for differences between
individuals in areas such as intelligence and language
ability. Dr. Paul Thompson from the University of California
at Los Angeles led the team. He writes in the journal
Nature Neuroscience: "We found that brain structure
is under significant genetic control, in a broad anatomical
region that includes frontal and language-related cortices.
"The quantity of frontal grey matter, in particular,
was most similar in individuals who were genetically
alike; intriguingly, these individual differences in
brain structure were tightly linked with individual
differences in IQ.
"The
resulting genetic brain maps reveal a strong relationship
between genes, brain structure and behavior, suggesting
that highly heritable aspects of brain structure may
be fundamental in determining individual differences
in cognition."
For
some time, scientists have suspected that grey matter
is the key to intelligence in the brain. However, this
is the first time the tissue has been studied with a
brain scanner and linked with IQ tests.
Professor
Robert Plomin of the Institute of Psychiatry in London
said that the amount of grey matter had to do with a
person's ability to solve certain problems. "Finding
a correlation between grey matter density and general
cognitive ability provides evidence for a biological
basis for it [IQ], though it's not necessarily causal,"
he said. However, the results do not rule out the chance
that studying could improve a person's grey matter.
Dr.
Thompson told the BBC: "A component of our problem solving
abilities is inherited, but it's only about 10-15% of
the variation in that trait, which means to say that
the effects of nurture, of learning - the non-genetic
factors - have tremendous importance in building brain
structure, intelligence and your performance in tests."
Source: BBC
Cosmiverse
Staff Writer
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