Historically psychologists have relied on a child's IQ to define and diagnose dyslexia, a brain-based learning disability that impairs a person's ability to read.
If children with poor reading abilities aren't diagnosed as dyslexic, they don't qualify for services that a typical dyslexic does, and they're not taught strategies to overcome specific problems in the way they view and process words.
But researchers at the Stanford University School of Medicine have said that this approach is not correct and claimed that IQ should not determine diagnosis of dyslexia.
Using an imaging technique, they have found that the brain activation patterns in children with poor reading skills and a low IQ are similar to those in poor readers with a typical IQ, and that their reading problems were not related to their general cognitive ability.
The work provides more definitive evidence about poor readers having similar kinds of difficulties regardless of their IQ.
These new findings provide "biological evidence that IQ should not be emphasized in the diagnosis of reading abilities," said Fumiko Hoeft, MD, Ph.D, an instructor at Stanford's Center for Interdisciplinary Brain Sciences Research, and senior author of the study.
"Convergent psychological, educational and now neurobiological evidence suggests that the long-standing and widely applied diagnosis of dyslexia by IQ discrepancy is not supported," the researchers stated.
Hoeft and her colleagues also point out that these and other findings indicate that, "any child with a reading difficulty, regardless of his or her general level of cognitive abilities (IQ), should be encouraged to seek reading intervention."
The study will appear in an upcoming issue of Psychological Science.