Cognitive Development and Mental Retardation

Dyslexia is not related to low IQ or mental retardation of any kind. Historically, dyslexia has always been defined as existing only among children with normal or above-normal intelligence, so in theory a low IQ negates a diagnosis of dyslexia. Children with low intellectual abilities will have difficulties that are generalized to all academic areas, as well as problems with day-to-day functioning at home. In cases of moderate to severe mental retardation, parents usually will be well aware of their child's limitations long before he is ready to attend school.

Reading Problems in Children with Low Intelligence

Children who have IQs considered to be merely below average or who are borderline mentally retarded may also have reading problems. Although these children may not fit the traditional profile of dyslexia, their poor reading ability can stem from the same underlying problems. Unfortunately, it is not always easy to get a clear diagnosis.

Many educators rely on a “discrepancy” test to diagnose dyslexia: they look for a significant gap between actual reading ability and the expected ability as determined from aptitude or IQ testing. However, recent research does not support this model. There is only a moderate correlation between IQ and reading ability, far less than the correlation between reading and early language development such as phonological awareness, which is now considered closely related to dyslexia. In other words, IQ can not reliably be used as a measure to predict reading skill.


Your child's “potential” cannot be measured with an IQ test. Research has shown that children with visual spatial learning styles, including dyslexia, tend to be “late bloomers.” Your child will become more capable over time as higher brain functions develop and he is able to better relate new learning to existing knowledge and experience.

Measurement of IQ can also be suspect in a child with dyslexia, as the tests of intelligence rely largely on the same sort of skills that are impaired in children with dyslexia, such as language interpretation and short-term memory. Many children perform lower on IQ tests because of their dyslexia. It is very common to see such children score much higher on IQ tests as they grow older, in part because over time they simply acquire the skills needed to understand the test.

Getting Help at School

The problem with comparing IQ scores to reading ability is that it leaves many children with reading disabilities unable to qualify for services such as additional tutoring or accommodations from their school district. If your child scores poorly on an IQ test, she may very well have exactly the same reading deficits as any other child with dyslexia, but be denied extra help and expected to function in the same classrooms with other children.

She may be labeled as merely being a “garden variety poor reader” or “low achiever.” In essence, she may be punished because she is not considered smart enough to have dyslexia.

Most educators now favor abandoning the discrepancy model and identifying dyslexia based on the characteristic pattern of weaknesses, rather than using an artificial standard of the perceived potential of the child. Thus, if your child has low IQ scores but does not seem to be cognitively impaired in areas other than those usually associated with dyslexia, you should understand that this book is for you. Your child will need the same extra help and will benefit from many of the same kinds of educational programs as any other child who is struggling to learn to read.

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