Dyslexia: Anomaly or normal variation?

This paper is an interim report on a large-scale survey. The background to the authors’ research into dyslexia is briefly outlined. Next comes an explication of the contrast between “anomaly” and “normal variation.” Some details are then provided of a survey of 12,905 children, age ten, who were given a variety of educational and cognitive tests relevant to a diagnosis of dyslexia. It is shown that the resultant distributions of scores are incompatible with the hypothesis of normal variation. The counter-hypothesis, viz. that dyslexia involves some kind of anomaly, has, therefore, to that extent resisted refutation. The 1980 CHES follow-up study was funded by grants from the Department of Health and Social Security, the Joseph Rowntree Memorial Trust, the Department of Education and Science, and the National Institutes of Health in the USA.