Mental Development Similar Among Boys, Girls

U.S. study is first major examination of typical changes through childhood

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HealthDay Reporter

FRIDAY, May 18, 2007 (HealthDay News) -- U.S. scientists are getting the first comprehensive look at how children's brains and behaviors change over time, and it's yielding some surprises.

It turns out that much-touted differences in the mental evolution of boys and girls aren't so pronounced after all.

On the other hand, the amount of money a child's family makes may have a big impact on his or her intellectual ability, with IQs rising alongside incomes.

Those are just the highlights of preliminary findings from a team of psychologists and psychiatrists at the U.S. National Institutes of Health. Their project, the National Institutes of Health MRI Study of Normal Brain Health, is assessing the neurological and behavioral development of 450 American children carefully selected to be free of problems and representing the diversity of the country's population.

"This is being done to learn more about the structural and functional development of the normal brain," explained Deborah P. Waber, associate professor of psychology at Children's Hospital Boston, lead author of the report. "The data will be used as baseline for all kinds of disorders of childhood brain development."

The first findings from the project were published Friday in the online edition of the Journal of the International Neuropsychological Society.

They include:

  • Mental performance differs little by gender. "We found a few significant differences that we would have suspected," Waber said. "For example, boys are better at visual and spatial tasks, and girls are better at motor speed, but there are no differences in many other paths, like memory."
  • Family income matters. Kids from more affluent homes do better than those from lower-income families, with average IQs of 105, 110 and 115, respectively, for children classified as low-, middle- and high-income. "But when we limit the groups to healthy children, the differences are not as great," Waber said. "That suggests that the difference has more to do with disparity in health care related to income."
  • Young children make the biggest gains. Mental performance climbed steadily from age 6, leveled off for most tests between age 10 and 12, and then improved only very slightly or not at all during adolescence, challenging the idea of a growth spurt in learning during the early teens.

In addition to undergoing three rounds of performance and behavioral tests as they aged, the children also underwent MRI and other scans of their brains to study the growth of different brain structures and the formation of neural connections. The scans also tracked changes in brain chemistry. Those images, and the information gleaned from them, will be made available to clinicians and scientists who study brain development.

There will be further reports, but "I don't think we are going to follow these children any further," Waber said. "This has been a very labor-intensive study at six sites across the country. It represents pretty much the limit of what our resources allow us to do."

No comparable study of normal cognitive development has ever been done, noted Judy Rumsey, the project officer who spearheaded the U.S. National Institute of Mental Health's participation in the project.

"This information will help determine what the developmental trajectories are and whether gender differences appear or disappear in the development of typically developing children up to 18 years of age -- children with no neurological disease, developmental disorder or psychiatric disorder," Rumsey said. "There has been nothing as comprehensive as this. It goes down to a very young age, with a sampling designed to insure diversity and representation for different social groups."

It is not possible to say just when the full range of images and information will be made available to professionals, Rumsey said. She said there still are some major issues to be settled, notably that of preserving the privacy of the young people who took part in the project.

More information

The project is described in detail by the U.S. National Institutes of Health.

SOURCES: Deborah P. Waber, Ph.D., associate professor, psychology, Children's Hospital Boston; Judy Rumsey, Ph.D., project officer, U.S. National Institute of Mental Health, Bethesda, Md.; May 18, 2007, Journal of the International Neuropsychological Society online

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