The Frontal Cortex

Adoption and IQ

Posted by Jonah Lehrer on July 26, 2006
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The NY Times Magazine described an interesting study that I’d never heard about before:

A study of French youngsters adopted between the ages of 4 and 6 shows the continuing interplay of nature and nurture. Those children had little going for them. Their I.Q.’s averaged 77, putting them near retardation. Most were abused or neglected as infants, then shunted from one foster home or institution to the next.

Nine years later, they retook the I.Q. tests, and contrary to the conventional belief that I.Q. is essentially stable, all of them did better. The amount they improved was directly related to the adopting family’s status. Children adopted by farmers and laborers had average I.Q. scores of 85.5; those placed with middle-class families had average scores of 92. The average I.Q. scores of youngsters placed in well-to-do homes climbed more than 20 points, to 98 — a jump from borderline retardation to a whisker below average. That is a huge difference — a person with an I.Q. of 77 couldn’t explain the rules of baseball, while an individual with a 98 I.Q. could actually manage a baseball team — and it can only be explained by pointing to variations in family circumstances.

That’s some amazing data. Either the IQ test is deeply flawed, or intelligence is less innate than we assumed (or, to put it more accurately, our genetic nature depends upon how we are nurtured). I hope this study encourages potential couples (especially rich couples) to contemplate adoption. Thanks to plasticity, our brain is never beyond redemption.

P.S. If I were a neuroeconomist, I would definitely want to know why rich parents tend to have kids with higher IQ scores. Is it more toys? Better schools? Less stress? Of course, trying to pick apart the mess of variables that we call childhood is a difficult task, but it’s certainly a question worth asking…

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Comments

  1. #1 Joe Shelby
    July 26, 2006

    How about, “the ability to take a test” is what was being measured? Children with no sense of focus or patience will perform more poorly, and focus and patience are both things that can be built up and are not necessarilly inate.

    In other words, their IQs might always have been higher, and they merely couldn’t “take the test” at that younger age.

    This is something that testers have to deal with when assessing performance and performance improvement, particularly with the increasing number of standardized tests – are the students better at the skills or better at taking tests.

    SAT scores from first test to second can vary by hundreds of points simply because of the comfort level of the test-taker.

  2. #2 William Dragoin
    July 26, 2006

    IS IT POSSIBLE THAT THE HIGHER STATUS PARENTS GOT “THE PICK OF THE LITTER.” SO TO SPEAK? PERHAPS, THE CHILDREN WERE “EQUAL” IN MEASURED IQ AT THE START, BUT VARIED IN OTHER WAYS (HEALTH,PERSONALITY? DIFFERENT HISTORY OF ABUSE?) THAT MIGHT HAVE ALLOWED THOSE DOING THE ADOPTING TO SEE GREATER POTENTIAL FOR DEVELOPMENT. WERE THE CHILDREN MATCHED ON VARIABLES OTHER THAN IQ?

  3. #3 mickster
    July 27, 2006

    Regarding rich parents having children with higher I.Q’s – this has to be to do with the way the children are treated – language which they are exposed to, their nutrition, etc. as ‘regression towards the mean’ states that the natural I.Q. of children with high I.Q. parents will be closer to the average.

  4. #4 FC
    July 27, 2006

    Was the adoptive parent’s IQ also tested and what’s the relationship between this and the child’s IQ? i.e. does parent’s relative wealth predict child’s increase in IQ better than the parent’s IQ?

    The average IQ has been increasing for years, and that must be due to environment.

  5. #5 Mark
    July 27, 2006

    I was just reading “Freakonomics” and Levitt’s theory was exactly the opposite. (That adoption did little to nothing to raise IQ scores) According to him, everything IQ related is due to the birth parents. I will forward him this story.

  6. #6 stewart
    July 31, 2006

    Jonah:
    Any IQ test is a mixture of knowledge (what you’ve learned), reasoning (how well you can learn or figure out something new), and speed (how quickly you perform these tasks). In general, IQ tests are highly reliable, especially in adults or over relatively short periods, meaning that scores are generally consistent from one time to another (within about .6 of a standard deviation 90% of the time, which is astonishing for any psychological measure).

    However, these characteristics can lead us to think that IQ scores must represent something relatively fixed and immutable. There’s no evidence this is the case. As FC pointed out, test performance has been increasing over the past 70 years (the Flynn effect), especially on measures of reasoning and thinking speed, and this is a huge effect, much larger than the difference between the highest and lowest social classes. This can only be an environmental effect, not a genetic effect. The single best predictor of children’s performance on an intelligence test is parental expectation for grades, more powerful than parental income or education. Again, this is a measure of home environment.
    Orphanages are depriving environments, with little warmth or personal attention. An increase in IQ after being placed with almost any family should be expected.
    For that matter, many psychology textbooks talk about the work of Skodak & Skeels (1949), who demonstrated that IQs of adopted children were related both to their birth mother but also their adoptive homes, and that IQs were markedly higher after changing circumstances. I recommend their work as a good start, and a reminder of how important the environment really is.

  7. #7 Miette
    August 11, 2006

    This is fascinating, as I just read the opposite in Freakanomics, and totally disagreed with it. Of course my disagreement is solely based on my experiences as an adoptee who knows their birth family as well, and speaks nothing for the IQ of the general population of adoptees. Thanks for linking to this study, it’s fascinating, and for anyone interested in reading more on the subject, I also recommend “The Developing Mind” by Daniel Siegel.

  8. #8 shamim
    January 29, 2008

    previous interventions on IQ, including the Head Start (Lee & Loeb, 1995 ) and High Scope (Schweinhart et al, 2005 ) projects and adoption (Skodak & Skeel, 1949 ; Fulker et al, 1988 ; Plomin et al., 1997 ; McGue et al, 1993 ), have only had temporary success, though the social benefits extend into adulthood (Schweinhart et al, 2005). i want research to see if intervention before the age of 3 has more permanent effect.

  9. #9 S Sherman
    September 12, 2011

    I am always thought about this, thanks for putting up.