It’s one thing to point out that programs to improve children's cognitive
functioning have had a dismal track record. We can always focus on
short-term improvements, blame the long-term failures on poor execution or lack
of follow-up and try, try again. It’s another to say that it's impossible to do
much to permanently improve children's intellectual ability through outside
interventions. But that’s increasingly where the data are pointing.
Two studies published this year have made life significantly more difficult
for those who continue to be optimists. The first one is by Florida State University’s Kevin
Beaver and five colleagues, who asked how much effect parenting has on IQ
independently of genes. The database they used, the National Longitudinal Study
of Adolescent Health, is large, nationally representative and highly regarded.
The measures of parenting included indicators for parental engagement,
attachment, involvement and permissiveness. The researchers controlled for age,
sex, race and neighborhood disadvantage. Their analytic model, which compares
adoptees with biological children, is powerful, and their statistical methods
are sophisticated and rigorous.
The answer to their question? Not much. “Taken together,” the authors write,
“the results … indicate that family and parenting characteristics are not
significant contributors to variations in IQ scores.” It gets worse: Some of the
slight effects they did find were in the “wrong” direction. For example,
maternal attachment was negatively associated with IQ in the children.
There’s nothing new in the finding that the home environment doesn’t explain
much about a child’s IQ after controlling for the parents’ IQ, but the quality
of the data and analysis in this study address many of the objections that the
environmentalists have raised about such results. Their scholarly wiggle-room
for disagreement is shrinking.
The second study breaks new ground. Six of its eight authors come
from King’s College London, home to what is probably the world’s leading center
for the study of the interplay among genes, environment and developmental
factors. The authors applied one of the powerful new methods enabled by the
decoding of the genome, “Genome-wide Complex Trait Analysis,” to ask how much
effect socioeconomic status has on IQ independently of genes. The technique does
not identify the causal role of specific genes, but rather enables researchers
to identify patterns that permit conclusions like the one they reached in this
study: “When genes associated with children’s IQ are identified, the same genes
will also be likely to be associated with family SES.” Specifically, the
researchers calculated that 94 percent of the correlation between socioeconomic
status and IQ was mediated by genes at age 7 and 56 percent at age 12.
How can parenting and socioeconomic status play such minor roles in
determining IQ, when scholars on all sides of the nature-nurture debate agree
that somewhere around half of the variation in IQ is environmental? The short
answer is that the environment that affects IQ doesn’t consist of the advantages
that most people have in mind -- parents who talk a lot to their toddlers, many
books in in the house for the older children, high-quality schools and the like.
Instead, studies over the past two decades have consistently found that an
amorphous thing called the “nonshared” environment accounts for most (in many
studies, nearly all) of the environmentally grounded variation. Scholars are
still trying to figure out what features of the nonshared environment are
important. Peers? Events in the womb? Accidents? We can be sure only of this:
The nonshared environment does not lend itself to policy interventions intended
to affect education, parenting, income or family structure.
The relevance of these findings goes beyond questions of public policy. As a
parent of four children who all turned out great (in my opinion), I’d like to
take some credit. With every new study telling me that I can’t legitimately do
so with regard to IQ or this or that personality trait, I try to come up with
something, anything, about my children for which I can still believe my
parenting made a positive difference. It’s hard. There’s no question that we
know how to physically and psychologically brutalize children so that they are
permanently damaged. But it increasingly appears that once we have provided
children with a merely OK environment, our contribution as parents and as
society is pretty much over. I’m with most of you: I viscerally resist that
conclusion. But my resistance is founded on a sustained triumph of hope over
evidence.
bloomberg.net
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