Writers often allow dyslexia a scientifically improper scope. Whatever symptoms or deficits they find, however disparate or infrequent, are claimed as indicative of dyslexia. Everything is subsumed. Try this translation of the immediately above:
‘One of the fascinations of Foot and Mouth Disease (FMD) for veterinarians is that, whatever one’s interest in bovine behaviour and performance, cattle with FMD will obligingly show interesting abnormalities in precisely that behaviour’.
If it were possible to say such a thing about FMD (it is not) one would be able to say, categorically, that FMD is either a collection of many syndromes which we have yet to distinguish from each other, or it is not a syndrome at all. No syndrome, however obliging, will show any and every symptom for which we look. We would know for certain, if this appeared to be so, that we were as yet too ignorant to say anything important about aetiology, effects or remediation. We would know that, as yet, we had no identified or understood syndrome to say such things about. We would treat our patient symptom by symptom, empirically, but be obliged to refrain from any diagnosis more precise than, say, ‘sickly cow’. To do otherwise would be hubris, not science. It would also block progress towards understanding, not advance it.
Definitions of developmental dyslexia are many and various, as Beaton et al observe. Some are so broad as to be almost meaningless, some are confused and imprecise, some say next to nothing. There is no consensus. A few examples will demonstrate this. The World Federation of Neurologists’ definition from 1968 was, for a couple of decades, the definition most widely quoted and some consensus gelled around it during that time. The WHO also defined thus in 1993. It goes like this:
Dyslexia is a disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity. It is dependent upon fundamental cognitive disabilities which are frequently of constitutional origin.
This may, though, be translated as:
‘Dyslexia is a difficulty with reading which may only be diagnosed if there are no other obvious causes to hand (such as poor schooling, poor parenting, low IQ or social disadvantage). It is caused by there being something wrong with the brain (well, very often, anyway).’
This uncertain definition is simply defining the syndrome as an odd difficulty with reading, given an otherwise apparently normal educational and social history. It almost amounts to a discrepancy definition (of which more later) and makes it impossible for a child from a socially deprived background to be ‘dyslexic’ at all.
The Dyslexia Institute (1989) defines ‘specific learning difficulty’ (which many use as synonymous with ‘dyslexia’) as follows:
Specific learning difficulties can be defined as organising or learning deficiencies which restrict the student’s competencies in information processing, in motor skills and working memory, so causing limitations in some or all of the skills of speech, reading, spelling, writing, essay writing, numeracy and behaviour.
This is so broad, invoking so many discrete and distinct cognitive domains, as to mean very little in fact. Are we to expect a ‘dyslexic’ to be defective in motor skills as well as information processing (whatever that means) and memory? Are we to believe that a ‘dyslexic’ with behavioural problems has these as a result of innate ‘organising and learning deficiencies’ (and what are these anyway and how will we recognise them?). If ‘dyslexics’ do not exhibit behavioural problems perhaps, or are not defective in, say, memory or motor skills, are they then no longer ‘dyslexic’ despite continuing poor literacy skills and difficulty in learning literacy?