Wednesday, March 29, 2006

Why Some Kids Are Smarter

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The greatest correlation was seen in the prefrontal cortex, which mediates planning and complex reasoning. "Intelligent children have a prolonged period of thickening in the prefrontal cortex. We wonder if this gives them an extended period to develop the complex circuitry to support high-level thought," says Shaw.

John Gabrieli, a neuroscientist at MIT, says the long-term duration of the study allowed scientists to uncover patterns not observable in previous studies, such as the delayed developmental trajectory for people who go on to score high on IQ. "If you tested just at age 7 or 14, you would have come to opposite conclusions," he says.

"It would be interesting to see how those trajectories evolve in kids with dyslexia or other learning disorders," Gabrieli adds. "Perhaps you could identify children at risk for learning disorders much earlier than we now do."

Shaw's team recently finished a similar study of children with ADHD, in which researchers looked for the brain changes that accompany spontaneous remission of the learning disorder. Shaw says the database of normal brain development helped interpret those findings, which they expect to release in a few months.

Richard Haier, a neuroscientist at the University of California, Irvine, who studies IQ, says the findings also raise the question: "What influences the development of this brain area to give some people a thicker cortex than others? Is it based on genetics or some interactions or experience that a young person has that may foster a thicker cortex?"

Shaw and his colleagues now plan to search for genetic variants that are linked to the pattern of cortical development, and hence IQ. Many studies have demonstrated that IQ has a strong genetic component, yet it's still unclear how those genetic differences manifest in the brain.

While this area of research has been contentious -- critics worry that knowing genetic determinants of IQ could lead to a deterministic attitude toward education -- experts say that IQ is most likely linked to a complex interaction of genetics and environment.

Shaw says it's still too soon to tell how much of the growth pattern is due to genetics and how much to the environment, or both. His team plans to investigate this question in future studies.

Why Some Kids Are Smarter

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