I am wondering if a child with a low IQ could have dyslexia? So much of what we've learned is that dyslexia is when kids with normal or high IQ scores struggle with reading and spelling. Our daughter was diagnosed with dyslexia, but others have told us she does not have it.

The thing is that over the past two years she has been doing the Barton tutoring and although her reading has improved, nothing else has. She is struggling in school more than ever.

She had testing for IQ done, but they could not give her a score because her subscores vary too much. But the scores they did give us were all in the 80s.

So is it just inherent that she would not have dyslexia? Or can a child have dyslexia and also a low IQ?

Dr. Pierson's Response: 

This is a very good question and one that's kind of tough to answer without knowing the specifics. Here is the operational definition of dyslexia [1]:

“Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by the difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.” (Lyon, Shaywitz, & Shaywitz, 2003, Annals of Dyslexia, p. 2)"

The part that I bolded has to do with your question. I diagnose dyslexia all the time. These students have receptive language skills that fall within or above the average range (typically on measures that fall between the 16-84th percentiles). When determining whether a child is dyslexic, I assess a student's receptive vocabulary, which has been found to be a good proxy for verbal intelligence. I then look at phonological (sound) processing skills, reading, spelling, and writing to determine whether weaknesses are in one or more of those areas in comparison to the strength in spoken language comprehension. Using this approach, a child with an IQ of 80 falls below the "average" range, and I would need scores at or below the 1st percentile in the other areas, particularly in phonological processing, to diagnose that child with dyslexia.

We always want a good comprehensive assessment of spoken language because oral language undergirds learning to read, spell, and write. A child with poor spoken language comprehension skills would be diagnosed with a language disorder and a subsequent reading disorder -- that profile is not dyslexic. And, in that case, intervention must focus on the understanding (and use) of spoken language as a priority in order to improve reading.

You did not say how old your daughter is. We can also see vocabulary scores in older children degrade over time because they have not had the same exposure to text as their peers. And, beginning about 4th grade, students are required to start using one's reading to learn (versus learning to read in the younger grades). Our kids with reading disorder are now at risk, because they simply cannot read the same texts; and they start to fall behind. Given that receptive vocabulary has been found to be a proxy for verbal intelligence, we need to be mindful of the fact that the vocabulary of older students may have degraded over time and not be truly representative of their capabilities.

A good diagnostic assessment by a professional who understands language disorder AND reading disorder/dyslexia should be able to parse this out for you. There is a challenge when testing and making diagnoses -- we are seeing a child, typically, in one day -- and he or she may not be having the best day. A good diagnostician will triangulate the data when making a diagnosis. We need to know student’s pattern of strengths and weaknesses.

Here [2] is what a comprehensive assessment entails.

Finally, IQ has been found to not be the best predictor of one’s potential. There are many people with “lower IQs” who accomplish more than many with high IQs. With good intervention, exposure to myriad experiences, and importantly, people who believe in her, your daughter has the potential to find her niche, be successful, and live a fulfilled life. I have experienced this with many of my clients over the years. She is lucky to have you advocating for her!