United States

According to the International Dyslexia Association (IDA):

Dyslexia is “a neurologically-based condition that affects word-level reading accuracy, reading fluency,  and spelling.  It is often described as an unexpected difficulty in learning to read”.

The formal definition of dyslexia given by the International Dyslexia Association is:

Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by 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.

Aiming to be clear and unambiguous, the IDA then provides commentary on some of the terms used in their formal defninition:

  1. ① ➼ “Dyslexia is a specific learning disability . . .“
    A learning disability simply reflects a natural variation in brain function that predicts an unexpected difficulty learning a skill valued by the culture in which the individual is expected to perform, in this case, the ability to easily learn how to read. As Samuel T. Orton said, for the person with dyslexia, “Intelligence does not correlate with reading skill.” In 2010, research done by Sally and Bennett Shaywitz concluded that “IQ is linked to the level of ability to read in the neurotypical individual, but is not linked to the level of ability to read in the dyslexic individual.” Dyslexia is no more an indication of disease or infirmity than would be a lack of musical or athletic talent.
  2. ② ➼ “… that is neurobiological in origin.”
    The deficit is intrinsic to the individual and occurs at the level of neuronal activity.
  3. ③ ➼ “It is characterized by difficulties with accurate and / or fluent word recognition and by poor spelling and decoding abilities.”
    This definition recognizes fluency, automaticity, and spelling along with decoding as being directly influenced by a deficit in the phonological component of language.
  4. ④ ➼ “These difficulties typically result from a deficit in the phonological component of language… ”
    The core deficit of dyslexia resides in the phonological system.
  5. ⑤ ➼ …that is often unexpected in relation to other cognitive abilities . . . ”
    The deficit involved exists in the presence of assets and is not expected as the result of a generalized developmental delay or disability. In 1902 James Hinshelwood indicated that “the problem is localized; it is not generalized to all areas of learning.” IQ is not a factor in diagnosing dyslexia. There is no truth to the assumption that persons of average or even limited intelligence can’t also have dyslexia. Dyslexia is an equal-opportunity deficit.
  6. ⑥ ➼ “and the provision of effective classroom instruction.”
    Individuals who can’t read due solely to poor instruction (curriculum casualties) do not have dyslexia. (Curriculum casualties, of which there are millions, could be virtually eradicated if every teacher had a working relationship with the IDA Knowledge and Practice Standards.)
  7. ⑦ ➼ “Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.”
    The primary goal of reading is to comprehend the meaning of text. The individual with dyslexia does not, without comorbid weakness, have a difficulty that directly impacts the ability to comprehend. However, if you can’t decode a word — you don’t have access to its meaning — and if you don’t read — the vocabulary and background knowledge necessary for efficient comprehension do not develop. Therefore, comprehension is a derivative and indirect casualty of not being able to identify words accurately.

After some discussion about their definition, the IDA concludes that:

The definition remains meaningful for research and for practice. It includes inclusionary criteria, which is critical. It does not specify operational criteria, which is impossible (i.e., thresholds for severity or eligibility). There should be no equating of dyslexia as a diagnosis and eligibility for special education because there must be a demonstration of educational need.”

They also provide simple graphic explanations of the changing nature of dyslexia understanding over the years:


The US National Institute of Neurological Disorders and Stroke states that:

Dyslexia is “a brain-based type of learning disability” that “specifically impairs a person’s ability to read”. Dyslexic subjects “typically read at levels significantly lower than expected despite having normal intelligence. Although the disorder varies from person to person, common characteristics among people with dyslexia are difficulty with phonological processing (the manipulation of sounds), spelling, and / or rapid visual-verbal responding”.

In individuals with adult onset of dyslexia, the Institute continues, it “usually occurs as a result of brain injury or in the context of dementia; this contrasts with individuals with dyslexia who simply were never identified as children or adolescents”.  Dyslexia can be inherited, and “recent studies have identified a number of genes that may predispose an individual to developing dyslexia”.

The American Dyslexia Association attempts to provide a “scholarly defninition”:

A dyslexic person of good or average intelligence perceives his environment in a different way, and his attention diminishes when confronted by letters or numbers. Due to a deficiency in his partial performances, his perception of these symbols differs from that by non-dyslexic people. This results in difficulties when learning to read, write and do arithmetic.

However, not all States in America have enacted dyslexia laws.

Taken from https://www.dyslegia.com/state-dyslexia-laws/

According to the US Department of Health and Human Services:

A learning disability — such as auditory processing disorder, dyslexia, and attention-deficit / hyperactivity disorder (ADHD) — can affect cognitive development. Challenges will differ based on the disability, but being aware of the issues can help adults link adolescents to the proper tools and resources so they can thrive.

The International Dyslexia Association adds that dyslexia varies in severity, and that its impact depends on the effectiveness of reading instruction and / or remediation.

However, gauging levels of severity is a complicated matter, made all the more complex in the US because of racial issues. The numbers of “White” and “Asian” 4th Grade children in the US whose reading levels are considered advanced far excede “Hispanic”, “Black”, and “First Nation” American children; while the numbers of 4th Graders from this latter group whose reading levels are considered “below basic” far excede those of “White” and “Asian” children in the same age group.

Furthermore, statistics show that children from different ethnic groups who perform poorly at school have differing chances of receiving special educational help, with 74% of white children receiving such help, and only 43% of Hispanic children being given the same intervention.

In other words, the likelihood of assistance for a dyslexic child in the US depends upon the combined factors of ethnicity and State geography – and this is before wealth and class are taken into account.

The IDA states that “about 13–14% of the school population nationwide has a handicapping condition that qualifies them for special education”. Current studies indicate that 50% of all the students who qualify for special education are “classified as having a learning disability (LD) (6–7%). About 85% of those students have a primary learning disability in reading and language processing”. Nevertheless, they argue, many more people — “perhaps as many as 15–20% of the population” — have some of the symptoms of dyslexia, including slow or inaccurate reading, poor spelling, poor writing, or mixing up similar words”.

According to the University of Michigan, US National Institute of Health research has shown that dyslexia affects 5-10% of the population, with estimates as high as 17%. Some people may have “mild” dyslexia, while others may “experience it more severely”. Dyslexia is one of the most common causes of reading difficulties in elementary school children. Only 10% of dyslexics will qualify for an IEP (Individual Education Plan)! The United States Department of Health and Human Services estimates that 15% of the U.S. population has dyslexia.

The difference in numbers between the lowest estimate of dyslexics in the USA and the highest estimates of dyslexics in the USA is 15% of the population – a staggering 49.5 million people.

15% difference represented as a proportion of the US flag

15% of the Stars missing…

15% of the population also looks like this

Or, in starker terms, 85% of the USA:

See for instance: