Dyslexia

The recently published Report of the Committee of Inquiry into the teaching of reading in schools (Bullock Report; see Department of Education & Science, 1975) discussed the large number of children who experience considerable difficulty in mastering reading, and concluded that 'there is a rather smaller group of children who experienced a difficulty in learning to read that cannot be accounted for by limited ability or by emotional or extraneous factors. The term "dyslexic" is commonly applied to those children. We believe that this term serves little useful purpose other than to draw attention to the fact that the problem of these children can be chronic and severe. It is not susceptible to precise operational definition; nor does it indicate any clearly defined course of treatment. ' Three years earlier, the Advisory Committee on Handicapped Children had reported to the Secretary of State for Education that 'the term "dyslexia" has been very loosely used in educational contents, and we do not consider it can usefully be employed for educational purposes. In particular, we cannot attach any scientific meaning to the term "acute dyslexia" and we are sceptical of the view that a "specific syndrome of developmental dyslexia" has been identified' (Department of Education & Science, 1972). This conclusion was loudly attacked by the growing lobby of parents of dyslexic children, and the same fate undoubtedly awaits the conclusions in the Bullock Report. What, then, are the controversies surrounding the concept of dyslexia which give rise to such heated argument? The first problem is that of definition. Without agreement on this, fuller investigations are doomed to failure. The World Foundation of Neurology's Research Group on Developmental Dyslexia defines it as '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' (Critchley, 1970). This type of definition is a negative rather than a positive one (Reid, 1968), in that once all children whose reading difficulty is associated with one of the major groups of factors presumably underlying the condition, the remaining ragbag is termed dyslexic. The above definition is a very rich clinical description of cases which undoubtedly exist, but in its present form it cannot be transformed into an operational definition which can be used in identifying groups of children for further study. The core concept underlying most writing on dyslexia is that of severe underachievement. It has become customary to differentiate between those children who, irrespective of their ability, are at the bottom end of a continuum of reading attainment (backward readers), and those who are underachieving in relation to their general level of intelligence {retarded readers). Dyslexia is sometimes regarded as a particular subcategory of reading retardation. Underachievement is, in many ways, a simple, attractive and common-sense notion. Unfortunately, there are many statistical pit-falls between the concept and its operationalization. Foremost among these is the effect of regression (Thorndike, 1963). If one simply subtracts a reading age from a mental age, the resulting figure is statistically biased so that very bright children are automatically seen to be underachieving, whilst very dull children appear to be overachieving. To avoid this statistical nonsense, sophisticated data analysis techniques have to be employed, and this has rarely been done in reading research (Yule, 1967; Yule et al., 1974). However, these techniques allow one to predict a reading age for any child knowing his age and intelligence. To the extent that the child's observed reading age falls below that which is predicted, the child can be said to be underachieving. At extreme degrees of underachievement, the child is said to have specific reading retardation (Rutter & Yule, 1973). The question is then: are dyslexia and specific reading retardation synonymous?