Cross-Cultural/Linguistic Differences in the Prevalence of Developmental Dyslexia and the Hypothesis of Granularity and Transparency

Developmental dyslexia is defined as a failure to acquire reading skills, despite adequate intelligence, education and sociocultural opportunity (Chrichey, 1975), and it is generally accepted that it is a neurobiological disorder with a genetic origin (e.g., Eden & Moat, 2002; Fisher & DeFries, 2002). It has been reported that up to 10 – 12% of children in the English speaking world suffer from developmental dyslexia (e.g., Shaywitz, Shaywitz, Fletcher, & Escobar, 1990; Snowling, 2000). Extensive research has been conducted in order to ascertain the causes of dyslexia (and subsequently to develop intervention programmes), since dyslexia sufferers form a large minority group, and yet there seems to be no consensus amongst the researchers as to what causes developmental dyslexia.