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New system of scoring IQ tests benefits children with intellectual disabilities


Researchers develop method which provides more accurate view of children’s potential

Parents of children with intellectual disabilities have long been frustrated by IQ testing that tells them little to nothing about their children’s long-term learning potential. That’s because the tests are scored according to the mean performance of children without disabilities, so the raw scores of many intellectually disabled children are converted to the lowest normalized score: typically a zero.

“We send back these reports that don’t tell parents anything about their child,” explained David Hessl, associate professor of clinical psychiatry at the University of California Davis M.I.N.D. Institute.

Now, Hessl and a team of collaborators have devised a new system of scoring IQ tests taken by children with fragile X syndrome, a genetic disorder that causes intellectual disabilities including autism. Their research1 has just been published online in Springer’s Journal of Neurodevelopmental Disorders.

“If this new method becomes widely available, we will be able to tell parents something more useful and more accurately diagnose and treat young children who are learning disabled,” said Hessl, a physician who cares for children with fragile X syndrome.

According to Hessl, there is a great deal of meaningful variability in the performance of children with intellectual disabilities on IQ tests. Frustrated by IQ tests’ lack of sensitivity, Hessl set out to devise a scoring method that would reveal the strengths and weaknesses of each child.

“I knew a more accurate estimation of the potential of these children would make a big difference in their lives,” he said.

Working with researchers at the M.I.N.D. Institute and Stanford University, as well as a statistician from Pennsylvania State University, the team came up with new normalized scores for 217 children with fragile X syndrome who had undergone IQ testing.

“The new scores tell us more precisely how a child with fragile X syndrome deviates from the normal population in every sub-test area,” Hessl said.

Treatment of fragile X syndrome depends on its manifestations in the individual, and range from behavioral therapy to medication. Widespread use of new normalized scores would allow physicians to better treat their patients.

Hessl concluded, “In the future, the publishers of IQ tests should include lower functioning individuals in their standardization studies. This might mean over-sampling those with intellectual disability in order to get more sensitivity, but it would help so many children.”

1. Hessl D et al. (2008) A solution to limitations of cognitive testing in children with intellectual disabilities: the case of fragile X syndrome. Journal of Neurodevelopmental Disorders. DOI 10.1007/s11689-008-9001-8

The full-text article is available to journalists as a pdf.


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