What is Dyslexia?

This posting takes the first step in examining dyslexia research – laying out the framework of what we will be looking at. A good place to start is the definition of dyslexia used by the International Dyslexia Association (IDA) and the National Institute of Child Health and Human Development (NICHD).

“Dyslexia is a specific learning disability that is neurological 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.”

This definition is carefully constructed, and the working group that developed it provides an excellent guide (Lyon, Shaywitz, & Shaywitz, 2002), however their definition presupposed that dyslexia is a disorder.  Even though that was the common understanding at the time, you can already sense their discomfort.

Let’s unpack this definition a bit ourselves, pointing to ideas we will explore in future postings.


Dyslexia is a specific learning disability that is neurological in origin. 

The word ‘dyslexia’ is drawn from the Latin dys + lexia to mean ‘bad at reading’.   Just so.

A ‘specific’ learning disability is specific to a single facet of understanding or using language and independent of broader learning issues such as low intelligence, family income, sensory impairment, etc. A well-defined learning disability has a distinct performance pattern, a distinct heritability pattern, and a distinct neuro-anatomical pattern.

The key idea is that dyslexia doesn’t leak over to other skills, it is ‘specific’ to reading and independent of broader learning issues. Dyslexia is indeed ‘specific’.  No one can tell if your child is dyslexic when they see him or her in the schoolyard. There is no IQ discrepancy, no brain damage, etc. A dyslexic child is an ordinary child, bright, perceptive, talented, but only can’t seem to learn to read.

But troublingly for researchers, dyslexia does not have ANY of the three features of a well-defined learning disability (Stanovich, 1996), and worse many ‘dyslexics’ walk away from their disability and become strong readers. To work around this, researchers argue there are two groups of impaired readers – true dyslexics who cannot learn, and ‘garden variety poor readers’ who will succeed with proper instruction (Gough & Tunmer, 1986). Their symptoms are identical, and the only way to tell them apart is to give them proper instruction and see whether they learn to read.  As we saw in the Torgesen Study, the number of true dyslexics may be vanishingly small.

Neurological origin means that dyslexia is related to the brain and nervous system, absolutely correct but there is no claim here that dyslexia is a neurological disorder. A functional ‘signature’ of dyslexia is clearly visible in a brain scan (Shaywitz & Shaywitz, 2008), but that simply means dyslexic readers use a different part of their brain. That makes perfect sense when you think about how a skilled reader decodes and a dyslexic reader uses memorized words and guessing-from-context.

There is no compelling evidence for a structural difference in a dyslexic’s brain, just different patterns of connections and functional usage representing a history of different learning. These are the same types of brain scan markings that musicians exhibit (Habib & Besson, 2009). Exactly what you would expect if reading was simply a skill that dyslexics had not yet learned.


It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities.

This sentence deftly cuts to the heart of the matter. Dyslexia is specifically a word-recognition deficit. Dyslexia is about reading (and writing), nothing to do with organizational skills or handwriting or math or telling time. And nothing to do with oral language, except that you need to speak English before you can make sense of reading English. We are specifically pointed to the word-recognition part of reading, not eye-tracking, grammar, comprehension, vocabulary, prosody, fluency, pragmatics, or the rest.

Of course dyslexics WILL have smaller vocabularies and an impoverished base of world knowledge to support comprehension, simply because they read less. Reading is like having a slow, thoughtful conversation with an author, and writing is a fundamental tool for thinking. High-level skills like language and intelligence are not innate, we acquire them through experience and practice, and most of our lifetime learning comes from reading.   Non-readers have a terrible risk of falling behind, of having their ‘specific’ learning disability blossom into a full-fledged LD.  They are limping and hobbled in the race to acquire intelligence.


These difficulties typically result from a deficit in the phonological component of language

The ‘phonological component of language’ refers to a very particular skill in blending and segmenting the sounds of speech, which is the basis for skilled reading (Liberman & Shankweiler, 1985). One of the most reliable claims in reading research is this: Blending and segmenting skills are correlated with reading ability.

A student without phonological skills must rely on memorized words and guessing, but that is really hard work. ‘Decoding’ is our bag of tricks for figuring out words that we don’t know, we look for clues in the spellings, morphemes, and etymology. We can also refer to context and guess at words, dyslexics rely heavily on guessing strategies but skilled readers find decoding is faster and easier. (West & Stanovich, 1978).

Dyslexic spelling tends to be awful because memory recognition (for reading) doesn’t automatically provide memory recall (for spelling).  The dyslexic student without segmenting skills cannot confidently break a word apart into sounds and then create a plausible spelling. You and I will say the word, even if just in our heads, and then write out the sounds. If we make a mistake, our spelling will still be close enough for a spell-checker.

Once your child starts reading with memorized words, he or she is in a trap.  Think about the correlation between phonological skills and reading. Your child won’t develop phonological skills from reading with memorized words or guessing from context, and without them his reading won’t improve. If he didn’t figure out blending and segmenting in grade 1, then he was  launched using the wrong strategy.  He is in terrible trouble, and nothing is going to get better unless he re-learns properly.

There is a discredited claim that phonological awareness is a developmental skill (ie: something that you grow into), and those who lack it therefore have a developmental disorder. Researchers have shown that skill in manipulating phonemes ONLY comes from learning to sound-out an alphabetic language (Read, Zhang, Nie, & Ding, 1986). It seems that you only gain phonological skills from learning to read properly.

If that’s the case, then all illiterates should show signs of dyslexic – and that was the finding of a study of illiterate Portuguese tested with phoneme deletion and addition tests (Morais, Cary, Alegria & Bertelson, 1979).  In post-war rural Portugal, the practice of poor families was to keep the oldest daughter from school to tend the younger siblings at home, and this pool of illiterate adults and their literate siblings provide a convenient population for minimizing the confounding influences of environment and genetics.  A brain-scan study showed that illiterates are indeed ‘dyslexic’ (Petersson, Reis, & Ingvar, 2001), supporting the proposition that the brain’s architecture is modulated by formal schooling, and especially by the intensive training involved in learning to read.

Lack of phonological skills prevents your child from becoming a skilled reader, but that statement is unhelpful.  The correct formulation is that your child urgently needs to be taught to read correctly, starting with blending and segmenting.

Many people confuse segmenting and blending skills with phonemic awareness and the quality of representation of phonemes in the brain. These are unrelated skills, infants as young as 1-month already show skilled phonemic discrimination (Eimas, 1971).


… often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction.

It’s not enough that a child can’t read, that failure must be unexpected. But if the child isn’t taught properly, then all bets are off. The problem is the term “effective classroom instruction”. Today our schools use a constructivist ‘whole language’ approach that lets children guide their own learning, and it works fairly well for most kids. But not all kids figure out how to read that way.

English is one of the trickiest languages to learn to read.   A study comparing how English and Germans learn to read (Wimmer & Goswami, 1994) found that normal English students must go through different strategies in their path to reading, first memorizing words, then switching to sounding-out, and then returning to skilled reading with memorized words. These aren’t clearly defined stages, and a child may be simultaneously using a beginner strategy for hard words and a more advanced strategy for easier ones.

German students typically skip the first step, which they can do because German spelling is very regular. The same researchers found that the slowest, most ‘dyslexic’ German student was both faster and more accurate than the best English readers, not because they are smarter or better taught but simply because their written language is easier to learn.

But here’s the thing, some percentage of English students don’t figure out the blending trick. They start with ‘beginner’ memorizing, and grimly keep at it. Maybe they are the best readers in grade 1. But there are over a million words in English, you can’t memorize them all. By grade 3 the wheels fall off. In grade 4 they are diagnosed with a learning disability.


Secondary consequences may include problems in reading comprehension…

The primary problem is word recognition – acquiring a sequence of correct words from the text. If word recognition is slow, inaccurate, or effortful, then comprehension will suffer. Reading with memorized words, guessing-from-context, and guessing-from-first-and-last-letters is much harder and slower than skilled decoding. Think of your child as having a 100-horsepower engine, if 50 of those horses are extracting words then only 50 are left to make sense of them.

Worse, if some of the words are wrong, then the story quickly stops making sense. The child hits a rot in the road (A what? Oh, a ‘rut’ in the road.) and loses his way through the story. For reading with comprehension, word recognition must be rapid, accurate, and effortless.


… and reduced reading experience that can impede growth of vocabulary and background knowledge.

The effect of practice on reading skill is called the ‘Matthew Effect’ (Stanovich, 1986), named after a verse in the biblical Gospel of Matthew, “The rich get richer, and the poor get poorer”.   Good readers tend to like to read and therefore tend to read more, and that practice improves their fluency, vocabulary, and background knowledge. Those assets make reading even more enjoyable, and so these ‘rich’ kids tend to read even more. Poor readers avoid reading. A small gap quickly becomes a yawning crevasse, and the poor readers are left hopelessly behind.



It is worth a moment to consider what has dropped from earlier definitions. There was an idea that dyslexia requires a discrepancy between IQ and achievement, thoroughly debunked (Siegel, 1992).  Speech perception in noise, debunked (Hazen, et. al., 2009).  Claims of familial and hereditary links, environmental explanations, and socioeconomic explanations didn’t stand up. The claims of co-morbidity, that children with dyslexia often have other difficulties like language, attention, math, motor, executive function, learning styles, etc., all unsupported. Left-right brain theories, visual deficits, auditory processing, and other attempts to explain dyslexia in medical terms, all happily gone.

All that is left are poor readers. Given proper instruction, they will learn to read. Some will be above average and some will remain below average, but only because that’s how averages work.

And the ones who don’t get help? They will remain dyslexic.  The current cohort of dyslexic grade-4 students will become next year’s cohort of dyslexic grade-5 students.



Over the next few postings, we will explore these ideas in more detail. But here’s the take-away: NOTHING WRONG WITH YOUR CHILD. Dyslexia is very serious, but repairable if you take action. Everything you need is on this website, and it’s all free.

Posted in Dyslexia Research

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