• A new brain-imaging study suggests that reading difficulties are the same regardless of overall intelligence.

    A new brain-imaging study suggests that reading difficulties are the same regardless of overall intelligence.

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Dyslexia independent of IQ

A new brain-imaging study suggests that reading difficulties are the same regardless of overall intelligence.

Brain-imaging study suggests that reading difficulties are the same regardless of overall intelligence — and that more children could benefit from support in school.

About 5 to 10 percent of American children are diagnosed as dyslexic. Historically, the label has been assigned to kids who are bright, even verbally articulate, but who struggle with reading — in short, whose high IQs mismatch their low reading scores. On the other hand, reading troubles in children with low IQs have traditionally been considered a byproduct of their general cognitive limitations, not a reading disorder in particular.

Now, a new brain-imaging study challenges this understanding of dyslexia. “We found that children who are poor readers have the same brain difficulty in processing the sounds of language whether they have a high or low IQ,” says John D. E. Gabrieli, MIT’s Grover Hermann Professor of Health Sciences and Technology and Cognitive Neuroscience, who performed the study with Fumiko Hoeft and colleagues at the Stanford University School of Medicine; Charles Hulme at York University in the U.K.; and Susan Whitfield-Gabrieli, also at MIT. “Reading difficulty is independent of other cognitive abilities.”

The study, which is forthcoming in the journal Psychological Science, could change how educators diagnose dyslexia, opening up reading support to more children who could benefit from it.

Rhymes and results

The researchers recruited 131 children, from 7 to 17 years old. According to a simple reading test and an IQ measure, each child was assigned to one of three groups: typical readers with typical IQs; poor readers with typical IQs; and poor readers with low IQs. All were shown pairs of words and asked to judge whether the words rhymed. (Rhymes are an effective way to probe dyslexics’ reading performance, since dyslexia is thought to entail difficulty connecting written words to sounds.) For some pairs, the researchers used words that rhyme but don’t share the same final letters — such as “bait” and “gate,” or “night” and “bite” — so that rhyme couldn’t be inferred simply from spelling. Using functional magnetic resonance imaging (fMRI), the researchers observed the activity in six brain regions known to be important for reading.

The results? Neural activity in the two groups of poor readers was indistinguishable. “The brain patterns could not have been more similar, whether the child had a high or low IQ,” Gabrieli says. Poor readers of all IQ levels showed significantly less brain activity in the six observed areas than typical readers, suggesting that reading difficulty is due to the same underlying neural mechanism, regardless of general cognitive ability.

Ditching diagnostic discrimination

The findings could have an important impact on both diagnosis and education for kids who struggle to read. Currently, Gabrieli says, many public school systems still require that a child have an otherwise normal IQ score to receive a diagnosis of dyslexia — essentially, that the label be reserved for children with a “reading difficulty that can’t be explained by anything else,” he says. But the new study suggests that even children with low IQ scores might benefit from treatment specific to dyslexia.

Jack Fletcher, a professor of psychology at the University of Houston Texas Medical Center Annex, says the study “adds to the evidence against” the notion that reading difficulty should be chalked up to general intellectual limitations in children with lower-than-average IQs. “Poor reading is poor reading,” he says. “IQ discrepancy doesn’t make much difference.”

Gabrieli, who says he hopes the new results will encourage educators to offer reading support to more struggling students, stresses the importance of diagnosing dyslexia and other behavioral disorders sooner rather than later. “Now, you basically diagnose dyslexia when a child seems miserable in school,” he says. “Maybe you could intervene before they ever get that way.”

Topics: Education, teaching, academics, Health sciences and technology, Learning, McGovern Institute, Neuroscience, Students, Brain and cognitive sciences


"about 5 to 10 percent of American children are diagnosed as dyslexic. Historically" Can you provide me with details of the source of this information?


Neil O'Gorman

I am glad to see another study about dyslexia and IQ not being related. I say another because there have been dozens of larger and better studies done going back over 10 years. The need for most MRI and dyslexia studies generally is limited to verification of already proven facts combined with the media and public's fairly common perception that they are more valid than interviews and paper testing. MRIs lack the resolution to determine individual results as normal dyslexia testing does but since much of the public won't believe anything about dyslexia until it is "proven" by MRI let's shout this old news from the roof tops.

The importance of the concept of dyslexia and IQ not being related is that lower IQ children have often improperly been excluded from consideration as being dyslexic and so are missing out on the opportunity of help that comes with being diagnosed dyslexic. Please read that long run-on sentence again. Presently dyslexic children with lower IQ's who could benefit from interventions as well as the smarter dyslexics are not being given the chance to be considered as dyslexic because of their lower IQs. That must be changed.

MRI studies are actually not the gold standard for information about dyslexia. Consider that all the children in MRI dyslexia studies are actually put into the different groups determined by standard pen and paper testing combined with oral tests.

I am at a loss as to why the media puts these MRI dyslexia studies as a source of primary information when they are really just supporting previous research conclusions. I posted an article in Aug/2006 that was based on years of earlier studies that basically said that dyslexia and IQ were not related. There were also some good studies that identified lower IQ dyslexics and determined that they benefited from dyslexia intervention as much as the higher IQ dyslexics did. Yes , those studies have already been done where lower IQ dyslexics have been diagnosed and given dyslexia interventions with the results that their improvements from interventions were similar to the higher IQ dyslexics given the same interventions.

Here is the article I wrote in 2006 dyslexiaglasses.com/dyslexia_m... . It was based on information available from many years before 2006.

I have a 8 year old daughter who was struggling at school in her reading. I was offered help for my daughter at a intensive reading class but my daughter had to undergo an iq test before she was able to be put in the class. After undergoing the test the result showed that my daughter had a low iq and was nolonger offered the help that she needed. Her local school told me that because of her low iq score they were unable to offer her any help and left in on me to get the help she needs out of school.

Overcoming Dyslexia, published in 2003 by Sally Shaywitz, M.D., read chapter 7. I am wondering why the above article doesn't reference the work of the Shaywitz' in terms of functional MRI's.

Also, As a final step in completing my Wilson Reading System Level 1 certification, I was fortunate to work with a student identified as having an intellectual disability. Initially, I was encouraged to select a student in the average IQ range. I resisted and the result was an eyeopening and successful (she advanced two grade levels in reading) experience, for the student and me.

My 6 year old was labeled as "severely disabled" by the school district. Now he is 10 and after reading intervention and home schooling, he loves to read. He had an IQ of 114 at age 6 even though he couldn't read. Now he can't get enough of books labeled 3 or 4 years above the normal reading level for his age. I have to make him stop reading every night. I'll bet his 114 IQ at age 6 was based on the fact that he just couldn't read. IQs do change over time, I'll bet. He now has a fabulous vocabulary and loves writing reports. He's in a small private school that meets 2 days/week and he has tons of fun with his friends on the 3 days it doesn't meet. I think he's developing a great emotional intelligence from this, too.

Thank you Emily for this great article. I love that you stress that "Poor reading is poor reading,” and “IQ discrepancy doesn’t make much difference.”

There are so many people who still do not fully understand what Dyslexia really is. If you are a parent who wants more information about dyslexia or reading in general, please check out the Dynaread knowledge base.

Dynaread offers a range of articles on subjects ranging from scientific research on Dyslexia, to How to’s and tips for helping children who struggle with reading and informational videos.

The link to the Dynaread knowledge base is https://dynaread.com/service/

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