by Ronald Kotulak, Chicago
Tribune, December 2, 2003
Impoverished children struggle under an invisible weight that often
crushes their intellectual potential, according to a growing body of
research that gives new insight into how environment shapes the developing
brain.
A recent University of Virginia study shows that poverty can erase a
number of points from a child's IQ score.
Another recent study found that inadequate nutrition early in life
combined with a lack of schooling can wipe out much of a child's potential
for learning. Good food and schooling can lead to substantial intellectual
gains in adulthood.
Both studies support a growing conviction among scientists that genes are
not immutable commandments dictating a child's mental potential. Instead,
gene function is highly dependent on environmental experiences,
underperforming in adverse circumstances and achieving their full
potential in favorable ones.
"We're finding that early life shapes the expression of genes," said
Reynaldo Martorell of Emory University, whose study of nutritional
supplements and early education appears in the current issue of
Pediatrics, a journal of the American Academy of Pediatrics. "You're born
with a range of possibilities and your early environment can shape how you
develop."
The findings of the IQ and environment study are sure to add fuel to the
long-standing and often bitter debate over which is more important for
mental development, genes or environment.
Nature-nurture debate
"There's a furious nature-nurture debate on this," said neurologist Paul
Thompson of the University of California, Los Angeles. "The genetics
people say IQ is a basic mental capacity that we largely inherit, like our
height or fingerprints. So it's very difficult to change your IQ.
"But this flies in the face of the wealth of new neuroscience studies
showing how changeable the brain is throughout life," Thompson said. "This
paper resolves that paradox. It is saying that your environment can have a
big impact on your IQ."
The findings are likely to be used in the debate over public policy,
especially the ongoing fight by the Bush administration to give states
control over the federal Head Start program.
"By showing that the environment in impoverished families makes a big
difference, that's of course exactly the environment that special programs
like Head Start are targeted at," said the study's lead author,
psychologist Eric Turkheimer of the University of Virginia.
The Virginia study is the first to compare large numbers of twins from
rich and poor families. It appears in the current issue of Psychological
Science, a publication of the American Psychological Society.
Its main finding: Poverty, lack of educational opportunities and other
deleterious environmental factors account for 80 percent of the decline in
IQ scores of very impoverished twins, scores that can be 40 points lower
than the IQ scores of twins from rich families who have maximum
environmental advantages.
Study may be a landmark
"These results, if they are replicated, will prove to be a landmark in the
study of intelligence," said psychologist Robert Sternberg, director of
Yale University's Center for the Psychology of Abilities, Competencies,
and Expertise. "It suggests that intelligence and its heritability cannot
be understood outside their environmental context."
Previous twin studies, which did not include poor and rich children,
served as the foundation for the "Bell Curve" and other writings
contending that if the environment children are raised in doesn't make any
difference for their IQ, efforts to improve the environment may have no
effect on raising intellectual achievement.
Twins are used to pull out differences between genes and environment
because identical twins have the same set of genes and tend to have
similar traits such as IQ. Fraternal twins share 50 percent of the same
genes; so their traits vary more broadly.
Turkheimer found that IQ scores among pairs of identical twins from richer
families were basically the same and that fraternal twins from richer
families averaged a 15-point difference between members of the same set.
But among the poorest twins, Turkheimer did not find that pattern. Instead
of finding a difference in the IQ levels of the fraternal twins he found
little or none, indicating that their environment was overwhelming the
ability of their genes to produce different intelligence abilities,
Turkheimer said.
"That not only makes sense, but it resolves some contradictory studies,"
said Thompson, who was not involved in the Virginia study. "If you are
rich, the chances are there is little you can do to affect your IQ, as you
have already optimized most of the factors that affect it [education,
nutrition, overall health, etc.]."
Children in impoverished families, on the other hand, often lack adequate
nutrition, talking, reading and other forms of normal mental stimulation
that genes need to build the brain circuitry for intelligence, he said.
Impoverished twins in the Virginia study lived in families whose average
annual income was less than $12,000, half the fathers were absent, 1 of 4
mothers had less than a ninth 9th grade education, and the children lived
in homes with two people to a room.
Nutrition, schooling study
In the Emory study, Martorell examined Guatemalan women who were given
nutritional supplements in the first two years of life and schooling
through the primary grades. Undernutrition and malnutrition are common in
Guatemalan children.
Re-examining the women in their 20s, Martorell found that those who had
received the supplements and schooling had academic achievement scores 33
percent higher than women who neither received supplements nor completed
primary school.
Primary education alone improved the achievement scores of women not given
nutrition supplements by about 20 percent, but the improvement increased
by another 50 percent among those receiving supplements as well as
education, Martorell said. "You're going to get quite a return on your
investment if you foster education," he said. "But if you also improve
nutrition in early childhood, your return will be magnified."
