What is Dyslexia?
Dyslexia simply means that a person has a persistent difficulty accurately decoding single words. It is a descriptive, not a diagnostic term. Unfortunately, the medical-sounding label implies that it is a distinct and identifiable reading disorder with a known medical cause. As Prof. Bishop points out, ''(M)edical-sounding terms are more successful memes than the descriptive terms because they convey a spurious sense of explanation, with foreign and medical-sounding labels lending some gravity to the situation...they are treated seriously and gain public recognition and research funding'' (Bishop 2010)

For a considerable length of time, one particular definition of dyslexia (IQ-achievement discrepancy where reading age was considerably lower than IQ would predict), was used as the basis for all diagnosis and research on the subject. It was eventually discredited: ''(T)here is little evidence that the long-term development of poor readers who are IQ–achievement discrepant is substantially different to that of poor readers who are not IQ–achievement discrepant, nor does IQ–achievement discrepancy reliably distinguish between those who are difficult to remediate and those who are more easily remediated. Consequently, IQ–achievement discrepancy is no longer the bedrock for identification of LD in the US (or of dyslexia in the UK, for that matter)'' (Singleton p17)

The demise of the IQ–achievement discrepancy definition created serious difficulties for those working in the specialist field of dyslexia. They needed another way to diagnose it; one that didn't require an IQ test. In the UK, the British Psychological Society (BPS) produced its own 'working definition' which it simplified to, ''(M)arked and persistent problems at the word level of the NLS curricular framework'' (BPS 2005 p20) The definition has ''no exclusionary criteria''. This working definition enabled professionals involved with 'dyslexia' assessment to carry on diagnosing the difficulty and allocating the label, if they wished, purely on the basis of subjective opinion or guesswork.

The British Psychological Society's definition of dyslexia (BPS 2005.p18) is, as the BPS itself acknowledges, only a 'working definition', not an operational one (BPS 2005 p19) It notes that, ''For a word to be used as a scientific concept, it must satisfy certain criteria'' but accepts that ''Currently dyslexia does not meet such stringent requirements'' (BPS 2005 p17)

''When something is operationally defined, this means it has parameters which can be measured with sufficient mathematical rigour that these measures can be relied upon to define the concept''
(D. McGuinness)

Response To Intervention (RTI) is another type of assessment which doesn't require an IQ test: ''A good indication of the severity and persistence of dyslexic difficulties can be gained by examining how the individual responds or has responded to well founded intervention'' (Rose 2009 p10). Unfortunately, when utilised for the purposes of dyslexia diagnosis or research, RTI is as imprecise and as questionable as the other forms of assessment and 'therein lies the rub'; without an internationally agreed "operational" definition of dyslexia - which is the first step in scientific research, meaning that there must be a precise (infallible) measure of what it is you're going to study, genuine diagnosis and empirical research cannot take place. This means, of course, that ALL past (and present) research that used the IQ-achievement discrepancy definition to select 'dyslexic' subjects is null and void, as is research based on any of the other many definitions -see Rice/Brooks appendix 1.p133.

''When reading literature claiming that ''dyslexics‟ exhibit this or that symptom, or behaviour, it obviously behoves us to ascertain how the sample of ''dyslexics‟ was arrived at – how were they diagnosed. If it was by the discrepancy model of diagnosis, as is almost always the case, the findings are thereby rendered invalid and should, properly, be ignored. They seldom are. Indeed, such findings regularly march cheerfully on, underpinning and ''validating‟ later work, in bibliography after bibliography. The ''borders of pseudoscience‟ indeed'' (Kerr p97)

''(M)uch thinking about dyslexia is almost wilfully sloppy and sloppy science never did anyone any good, very particularly the subjects of it'' (Kerr.p93)

Meanwhile, many eminent figures working in the wider field of education and literacy continue to state that, at present, there is no scientifically accurate way to differentiate between those with a special reading disability, ‘dyslexia’, and ordinary, 'common garden' poor readers:

- “I’m sorry, I have no idea what dyslexia is” (Prof. Pamela Snow)

- ''The underlying difficulty appears to be the same, the way these children respond to treatment appears to be the same, there appears to be no justification whatsoever for going in and trying to carve out a special group of poor readers. This is what 15 years of research, all over the world has shown can’t be justified on a scientific or empirical basis'' (Prof.Stanovich in Mills. The Dyslexia Myth)

- ''Most people assume that dyslexia is a clearcut syndrome with a known medical cause, and that affected individuals can be clearly differentiated from other poor readers whose problems are due to poor teaching or low intelligence. In fact, that is not the case.'' (Prof. Bishop 2010)

- ''Because there is no way to differentiate students with learning disabilities, the label is meaningless'' (Prof. George Cunningham)

- "It is a dimension, it is more or less of something. There is no dividing line where you have it or do not. There is nothing to diagnose." (Prof. Plomin. TES. 2019)

- ''(A)ttempts to distinguish between categories of ‘dyslexia’ and ‘poor reader’ or ‘reading disabled’ are scientifically unsupportable, arbitrary and thus potentially discriminatory'' (Prof. Elliott/Dr.Gibbs).

- “There is no agreed-upon prevalence figure; that's why we should not be talking about dyslexia as if it were a well-defined diagnosis for a well-defined group. I use the word as a descriptor for word-level reading difficulties...” (Dr. Louisa Moats)

- ''In our present state of knowledge it does not seem helpful for teachers to think of some literacy learners as 'dyslexics' and others as 'ordinary poor readers'' (Dr.Rice/Prof.Brooks)

- ''They learned what they were taught, period. There are no dyslexic kids. I mean, that is just a myth'' (Prof. Engelmann. Childrenofthecode interview)

There is no need to manufacture an innate and incurable brain defect or difference to explain the widespread difficulties children living in English-speaking countries have with learning to decode and spell. The evidence-based explanation is clear and simple: "The cross-cultural comparisons reveal that the source of English-speaking children's difficulties in learning to read and spell is the English spelling system and the way it is taught. These comparisons provide irrefutable evidence that a biological theory of "dyslexia'', a deficit presumed to be a property of the child is untenable, ruling out the popular "phonological-deficit theory" of dyslexia. For a biological theory to be accurate, dyslexia would have to occur at the same rate in all populations. Otherwise, some type of genetic abnormality would be specific to people who learn an English alphabet code and be absent in people who live in countries with a transparent alphabet, where poor readers are rare. A disorder entirely tied to a particular alphabetic writing system is patently absurd and has no scientific basis. English-speaking children have trouble learning to read and spell because of our complex spelling code and because of current teaching methods, not because of aberrant genes'' (D.McGuinness ERI p3. bold added.)

''(C)hildren with general language delays, weak auditory or verbal short-term memory, or other perceptual and cognitive deficits could have problems learning to read and spell.  But these are language and memory problems, not ''reading disorder'' [dyslexia] problems.  These children are few and far between, constituting less than 5% of the population'' (D. McGuinness RRF messageboard)

The first study to show clearly that dyslexia is due to 'the English spelling system and the way it is taught' was that done by Heinz Wimmer in Austria (1993). German is spoken in Austria. It has a transparent written code and is taught using synthetic phonics. Wimmer tested all the worst readers in Salzburg sent to him by their teachers and found that they scored 100% correct on reading accuracy and nearly as well in spelling. Their only difficult was in reading speed. Next, Wimmer collaborated with an English researcher Goswami (1994). They compared normal readers in Salzburg (7 yr.olds with 1 yr. of instruction) and London (9 yr.olds with 4-5 yrs. of instruction) reading comparable material. The Austrian children read the material as fluently and accurately as the English 9 yr.olds and made half as many errors. A third study by the researchers Landerl, Wimmer and Frith (1997) compared Austrian 'dyslexic' children (slow readers) with English 'dyslexic' children (very inaccurate readers and spellers). The Austrian 'dyslexics' were not only far more accurate but also read twice as fast as the English dyslexics.

The empirical evidence suggests that dyslexia (very slow and very inaccurate decoding and spelling) occurs in a significant percentage of children in English-speaking countries when they need to learn what is an extremely opaque orthography without comprehensive instruction in the English alphabet code. When high quality synthetic phonics teaching is absent, incomplete, muddled or delayed many children do, luckily (and amazingly), still discover the alphabetic code for themselves, but those who fail to do so will, out of necessity, have to form their own strategies to access the code.

Dyslexia due to poor teaching occurs in all social classes and, as Tom Burkard of the Promethean Trust says, ''There would not be such a huge industry charging obscene amounts of cash to (supposedly) remedy reading failure if it were not just as common with middle-class kids as with others.''(Burkard. RRF messageboard 20/12/04) Ruth Miskin, early reading expert and past headteacher, warns parents, ''We’re not talking about poor kids here, from homes where televisions are always on. I’ve seen plenty of kids from affluent families,... pupils at private schools, the 4x4 parked in the drive. These children are often labelled dyslexic or SEN (with special educational needs). Not a bit of it: what they are is, to borrow an American acronym, ABT — ain’t being taught'' (Miskin)

''So it is mainly the middle class children - whose parents believe government propaganda about improving schools, or who buy poor-quality private schooling in the sad belief that the writing of a cheque guarantees quality teaching - who get involved in the great 'dyslexia' fantasy. They know that something is wrong. The 'dyslexia' lobby persuades them that it is their children who are at fault. This helps relieve parents and schools of any responsibility for the problem. The children, too, are led to believe that they are in the grip of some force that is beyond their control. This is why so many people willingly co-operate in their own victimhood.'' (Hitchens. MailonSunday 04/06/07)

Early difficulties with single word decoding as a result of poor, absent or delayed instruction lead extremely quickly to generalised cognitive, behavioural, and motivational problems:
''(S)kill at spelling-to-sound mapping (must) be in place early in the child's development, because their absence can initiate a causal chain of escalating negative side effects ... extremely large differences in reading practice begin to emerge as early as the middle of the first-grade year''(Stanovich p 162)

'Distinguishing cause from effect – many deficits associated with developmental dyslexia may be a consequence of reduced and suboptimal reading experience’

The dyslexia pandemic: a tale of blame and no blame.

Prof.Pamela Snow: Dyslexia? We need to talk.

Prof. Pamela Snow: Dyslexia Dystopia.

Why do some children struggle with reading?

Reading difficulty is a teaching problem not an intelligence problem
''(I)f a child leaves school unable to decode fluently it is the school’s fault'' N.B David Didau restricts his comments on decoding ''to children in mainstream school within the normal ability range''

Prof. Julian Elliott:
The dyslexia debate: some key myths

Prof. Julian Elliott: The end of dyslexia?

D. McGuinness: submission to the UK Parliament inquiry into reading interventions and dyslexia (LI13)

Hugo Kerr: Ch8. Dyslexia

D.McGuinness' critique of Goswami's TES article on 'dyslexia' across different languages.

Developmental dyslexia in adults: a research review

RTI: Response to Intervention or Really Terrible Instruction?

The irrelevance of intelligence testing for reading disability/dyslexia issues

Landerl, Wimmer & Frith: The impact of orthographic consistency on dyslexia: A German-English comparison

See p23-30 for the House of Commons cross-party Science and Technology committee's 'evidence check' report on Dyslexia

Secondary English teacher, blogger and author David Didau asks: Does Dyslexia Exist?

In D.McGuinness's response to Hulme she describes the problem with 'dyslexia' research studies.
See D.McGuinness. Language Development and Learning to Read p10-11 for an outline of the faulty ''isolated-groups design'' commonly used for 'dyslexia' studies.