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From NPR News this is ALL THING CONSIDERED, I'm Melissa Block.
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And I'm Michele Norris. It usually makes parents proud when their children reach a developmental milestone ahead of other kids. But when it comes to intelligence, researchers say the smartest children appear to have brains that develop later. NPR's Jon Hamilton explains.
JON HAMILTON: Researchers at the National Institutes of Health have been tracking brain development in several hundred children since the 1980's. The kids get an MRI scan every couple of years and computers analyze the result. One goal is to find the link between specific changes in the brain and intelligence. At least the kind that can be measured. So a group of researchers has been studying the cortex, or gray matter, that makes up the brain's outer layer. This is where so-called high level thinking takes place. Dr. Judith Rapoport says they expected to find evidence that a thicker cortex meant a higher IQ, but they didn't.
JUDITH RAPOPORT: When we looked at the very youngest group, the four to eight year olds, it was confusing. It looked like it was telling you that thinner brains had higher IQ.
HAMILTON: To figure out what was going on, the team looked at how the scans changed as these children grew up. Rapoport says they divided the children into three groups according to intelligence.
RAPOPORT: The very, very brightest third had a later development of their cortex so that at the earlier ages they hadn't really started really growing to their peak amount yet.
HAMILTON: The cortex in these children started thinner, but grew faster and for a longer time. By at about age 11 it was actually thicker than the cortex of less intelligent children. The research appears in this week's issue of the journal Nature. Rapoport says the results challenge an assumption made by many parents.
RAPOPORT: People are usually preoccupied with everything happening earlier, and that the brightest being able to do things in a precocious way. And this suggests that there could be some very clear advantages to things happening later.
HAMILTON: One is that if the brain keeps growing into adolescence it can be shaped in response to more complicated experiences and ideas. The research does not settle another concern parents have, the link between intelligence and genes. Richard Passingham is a neuroscientist at Oxford University in the U.K. He says it would be easy to look at this study and conclude that intelligence is predetermined by how your brain grows.
RICHARD PASSINGHAM: You might naively just think, oh, that must be because there are differences in the genes compared with those of lesser intelligence.
HAMILTON: He can imagine parents seeing the study and thinking...
PASSINGHAM: Oh dear, it's all the brain, therefore there's nothing we as parents can do about it.
HAMILTON: But Passingham says genes aren't the only explanation for smart kids.
PASSINGHAM: It's possible that those with superior intelligence, and live in families in which there are also people with superior intelligence, and thus there is a richer linguistic and social environment. Now I'm not saying that is the explanation, I'm just saying it's not ruled out.
HAMILTON: Passingham says intelligence depends on the right mix of nature and nurture. Genes might determine whether a child's brain develops later, but that won't make the child smarter unless the brain also gets the right kind of stimulation. During childhood, every experience helps shape the brain and determine its abilities. Passingham says the study makes the case for paying more attention to a child's surroundings, not less.
PASSINGHAM: What you would do is advise teachers, parents and everybody else to produce a stimulating social and linguistic environment as possible.
HAMILTON: That can be especially difficult for children who are extremely intelligent. Studies suggest that talented and gifted kids are more likely to drop out of school because of boredom.
Jon Hamilton, NPR News.