Who exactly is dyslexic, and who is to say?
To begin with, very few people are actually assessed as "dyslexic". It is more usual for a psychologist or other assessor to come up with an opinion that a pattern in test results, at times combined with an analysis of actual performance, is "consistent with" such an assessment. This is a phrase widely used in the medical profession when a doctor can't be sure.
Virtually every test score that meets this vague criterion includes a weakness in memory. Most include a weakness in recognising words, and in recognising words presented at speed - also a weakness in memory, as the words need to be built up from their constituent parts.
The point at which a combination of weaknesses leads to a "category" judgement is never certain. Categories bring supposed benefits, and, some people say, comfort, in that they understand the issues more clearly.
But do they? And, in particular, does the category of dyslexia (hereafter dx)?
I no longer believe it does. Dx is a concept of the late nineteenth-century, when our knowledge of the brain and its operations was far less developed than it is now. At the time, it served a useful purpose in isolating particular difficulties with reading from general learning difficulties that had their own categories, usually socially and intellectually pejorative. More recently, it has come to be used as an umbrella term, which can be extended to cover just about any difficulty with reading except those caused by visual stress - which is itself confusing, as visual stress can cause symptoms that are closely associated with dx.
But let's get back to the hard evidence. If someone has a weakness in short term memory, they can learn to use their memory more effectively, for example by learning to group similar words, and so form artificially the neural networks that immediately successful readers form naturally. If they have difficulty in reading fluently, the task can be broken down and rebuilt, like a music lesson, so that the obstacles to fluency can be identified and tackled. If they have problems with spelling, which is perfectly natural in English (see D Crystal, Spell it Out, for the reasons why) then they can be taught to spell.
In each case, the hard evidence of a particular cause of difficulty is more descriptive of the problem, and more indicative of its solution, than the umberlla term. This is important, not just because the term creates a sense of victimhood and helplessness, but because, against all intention, it actually gets in the way of designing the teaching that the individual needs. At present I never use the term dx unless someone else does first. We would have a much clearer view of the situation, and the action that is needed, if this practice were adopted by everyone else, and dx seen as a historical, rather than a modern scientific concept.