and Nurture Influence I.Q.
YORK (Reuters Health) - Hoping to resolve the question of where
intelligence comes from, researchers now suggest that a person's
intelligence quotient, or IQ, is the outcome of a continuous circle
of influence involving both genes and environment--and that the
measure is fluid over a lifetime.
a whole lot of traits--including IQ--have been shown to be highly
heritable, much of the effect of genes may come from the way genes
seek out good environments,'' said study lead author William T.
Dickens of the Brookings Institution in Washington, DC.
his colleague James R. Flynn of the University of Otago in New
Zealand developed a new mathematical model to unravel the complexity
of the nature-nurture interaction. Reporting in the April issue
of Psychological Review, the researchers note that a relatively
small change in the environment can have a very large and quick
impact on IQ, but that such impacts may prove to be short-lasting.
In this regard,
Dickens and Flynn stressed that those who attempt to manipulate
the cycle by adjusting the environment will find the process tricky
and elusive. They noted, for example, that parents who place a
child in a challenging pre-kindergarten setting may indeed observe
a fast rise in their child's IQ. However, they will just as often
find that the child's gains are lost once he or she leaves the
environment, if the one that replaces it is less demanding and
Dickens and Flynn found that seemingly small environmental triggers
play a large--if changing--role in influencing an individual's
IQ. In what the researchers suggest is a snowball effect, a person
who is perhaps only slightly more genetically ``gifted'' than
average may have easier access to social and work situations that
involve higher-than-average degrees of intellectual stimulation.
will then be motivated to seek out more of the same, they noted.
He or she will perhaps set a higher bar for educational and job-related
pursuits, which will put them in contact with like-minded people.
And the result, according to the researchers, is an upward spiral
of IQ that is driven by both genes and circumstance.
is that if you have a small genetic difference between two people,
it can be blown up by this process,'' Dickens told Reuters Health.
``A small initial advantage in something like IQ leads to an environment
that benefits that trait, which leads to a better IQ, which leads
to a better environment and so on.''
however, that the role of environment can and does shrink as a
person ages--with their genetic predisposition taking greater
prominence as individuals move outside the more controlled environment
of their early years and into a setting of their own choosing
and interests. As proof of this development, he and his colleague
point to the experience of adopted siblings who have different
biological parents. They noted that as they age and leave home,
such siblings' IQs often differentiate and more closely resemble
their genetic roots.
Psychological Review 2001;2:1-
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