Ask the average ‘man on the street’ about dyslexia and the reply that you will probably get is, “Oh yes, that’s when you muddle up your b’s and d’s.” This simplistic definition has led to people seeing dyslexia as a visual condition, where the dyslexic’s brain is unable to recognise the spatial orientation of various letters. However, for the vast majority of dyslexics, the truth is that their difficulties are more rooted in the sounds of language than the symbols that represent those sounds. In the case of the b’s and d’s, the similarity in the sounds /p/, /b/ and /d/ result in children who have difficulty processing sounds being unable to distinguish between them. These children do not muddle up their b’s and d’s, they simply can’t hear the difference between them.
In 1994, a workgroup of the International Dyslexia Association, which included such luminaries as Reid Lyon, Sally Shaywitz and Louisa Moats, came up with the following definition of dyslexia. This definition (represented in the graphic below) was simple and easy to explain.
Insufficient phonological processing resulted in difficulty with single-word decoding that, in turn, caused difficulties in reading, writing, and spelling.
This rather simplistic definition was refined in 2002 to:
Dyslexia is a specific learning disability that is neurobiological in origin. It is characterised 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 the growth of vocabulary and background knowledge.