Issues in diagnosing dyslexia

Since the first descriptions of children with congenital word blindness or dyslexia, the proper criteria for diagnosis of dyslexia have been debated. Issues in this debate concern, among others, the role of underlying causes of reading and spelling and the use of a discrepancy between reading ability and intelligence. This chapter will consider recent evidence from family risk studies of dyslexia that speaks to these issues. We conclude that current evidence on the etiology of developmental disorders neither supports a specific underlying cognitive profile (e.g., phonological deficits), nor the requirement of a discrepancy with intelligence. Deciding factors in diagnosis should be lack of learning opportunity, other exclusion factors, and naturally the degree of reading and spelling difficulties.