While below average dyslexics may be harder to identify that does not mean they could not be helped by proper intervention. The result of this false belief is that dyslexics that could be helped are never identified.
After searching the Internet , I have found why this is such a common belief.
Everybody says so -
A review of many pages of dyslexia web sites indicates that almost all say dyslexics have normal or above normal intelligence. ( This seems to be enough for some people but I usually require at least anecdotal evidence )
By Definition -
Dyslexia is considered a learning disability in the Federal Register under Public Law 94-142. As with other learning disabilities covered under this law, dyslexia involves what is called an exclusionary diagnosis. That is, instead of describing characteristics directly, the definition describes all the conditions that must be ruled out (e.g., low IQ, physical handicaps, environmental factors, etc.) before making a diagnosis. ( This carries more weight than everybody says so. This is a case of I say so and I make the rules. The agenda here seems to be to limit who will be able to get added money from school resources.)
There are other definitions for dyslexia and learning disabilities. I tend to think this next source's agenda is more directly related to scientific reality.
The term "learning disability" was apparently first used and defined by Kirk (1962, cited in Streissguth, Bookstein, Sampson, & Barr, 1993, p.144). The term referred to a discrepancy between a child’s apparent capacity to learn and his or her level of achievement. A review of the LD classifications for 49 of 50 states revealed that 28 of the states included IQ/Achievement discrepancy criteria in their LD guidelines (Ibid., citing Frankenberger & Harper, 1987). However, the National Joint Committee for Learning Disabilities (NJCLD) (1981; 1985) preferred a slightly different definition: "Learning Disability" is a generic term that refers to a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to Central Nervous System Dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g. sensory impairment, mental retardation, social and emotional disturbance) or environmental influences (e.g. cultural differences, insufficient/inappropriate instruction, psychogenic factors) it is not the direct result of those conditions or influences.
Another reason for believing dyslexics are above average is not that they are but only that they are easier to detect.
Current National Institutes of Health (NIH) studies estimate the prevalence of this disorder (dyslexia) at 20% of school age children. This means that one in five children have the fears and emotions expressed above. It is by far the most common form of learning disability. In addition, dyslexia affects all socio-economic classes and all races equally (2) (2). It affects as many boys as girls (3). However, boys are usually spotted more quickly because they tend to exhibit externalizing behaviors such as acting out when doing poorly in school. Consequently the teacher is more likely to look for a problem in a child who is acting out in class rather than one who is quiet. Thus, boys who tend to act out more will be noticed more by the teacher.
As described above, children with the disorder often feel stupid as a result of their constant struggle in school. However, there is no correlation between intelligence and dyslexia. Furthermore it is important to note that phonological abilities do not depend on IQ - the genetic risk can affect learning to read in children of high and of low IQ equally though the problem is easier to detect in those of higher ability who do not show other learning problems. This does not mean however, that it will be easy to differentiate at school entry
between children with dyslexia and children at risk of failure because they come to school from socio-economically or linguistically disadvantaged backgrounds.
Has anyone actually looked to see if low IQ children would benefit from reading intervention compared to higher IQ children?
There's now evidence from research at York University that shows - contrary to what you might have expected - that children with a low IQ can be helped just as much with reading problems as children with a high IQ, providing it's the right reading programme and providing it's implemented in the right way. What you might have expected is that children with a low IQ wouldn't progress as quickly as children with a high IQ: but what these studies in York have found, he says, is that they do.
This isn't a complete review of the subject and I should add that some researchers have looked at dyslexics V's non dyslexics and indeed concluded that dyslexics are of average or above average intelligence. The flaw I see is in those comparisons is that the group of dyslexics does not actually represent all dyslexics but rather diagnosed dyslexics. As the NIH says, the higher intelligent dyslexics are easier to identify and therefore I believe they are over represented in the groups of dyslexics that are compared. If you consider the fact that there also does not seem to be any real difference between the prevalence of dyslexia in boys and girls but more boys are identified as having dyslexia because they seem to act out their frustration more often, then the resulting ,everybody says so , that dyslexia occurs more often in boys than girls starts to be explained in a similar manner.
My little niche in the field of dyslexia involves visual dyslexia. I would like to give one anecdotal example of a undiagnosed visual dyslexic who was considered mildly mentally retarded. It is about the saddest waste of potential I have ever experienced.
Briefly, I accidentally discovered filters that seemed to remove visual problems for a dyslexic back in 1992. After reading all the literature and seeing how badly everyone thought about tinted lenses as a solution I really didn't want to get involved.
My girlfriend's son seemed to meet the description of reading below his intelligence level for being dyslexic as he was a 20 years old special ed student and had never written or read a word in his life except his name and still did not know his alphabet. He was classified as being mildly retarded, had cerebral palsy affecting his left side and had some hearing loss.
Being bored one day, I thought to see if the filters that later became the See Right Dyslexia Glasses might help Chris. It wasn't readily apparent how to go about that but eventually I tried writing out the alphabet once in order and below that I scrambled the letters. I asked him to match A-A and B-B etc. He could only match 13 of the letters. That did seem to help explain why he never learned his alphabet or to read.
After putting on the See Right Dyslexia Glasses he could match all 26 letters and in 3 days he could read the alphabet from flash cards. He wrote his first note to his mother after a week. Since then I have been looking for the research that has been done to conclude that dyslexics are only from the group of average to above average intelligence and I still do not believe it has ever been done.
My experience with how Chris responded to the dyslexia glasses motivated me to investigate several subjects. The first was to identify who the See Right Dyslexia Glasses might help and why. The second was to identify why dyslexics were thought to be from the group of people who have average to above average intelligence.
15 years later I have the answers to both questions. The See Right Dyslexia Glasses remove any described visual problem that makes reading difficult for visual dyslexics and so benefit any dyslexic that can describe a visual problem that makes it difficult to read. The myth of why dyslexics are considered to have average or above intelligence is the result of several factors described in this post but does not seem to have any valid support and is a self fulfilling prophecy.