The Prevalence of Dyslexia: A New Approach to Its Estimation

This study proposes a new approach to operationalizing dyslexia in prevalence estimates:

• As noted in the article, the International Dyslexia Association specifies that:
  • Dyslexia is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities.
  • These difficulties are often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction.
• To capture the "unexpected" nature of dyslexia, this study operationalizes dyslexia as a substantial difference between an individual's listening comprehension and reading (1.5 SDs).

A model-based meta-analysis and simulation based on this definition found:

• Individuals with a substantial difference between their listening and reading comprehension can be found throughout the reading ability spectrum.
• Some individuals with a substantial difference in listening and reading comprehension may not exhibit low reading performance.
• In a sample of poor readers (below the 20th percentile), most readers will not be expected to have dyslexia because they will have similar levels of listening and reading comprehension ability.