The terms ‘reading disabilities’ and ‘dyslexia’ are used here synonymously. Dyslexia has many different definitions. According to the National Institutes of Health, the research definition of dyslexia is that it is a specific learning disability of neurological origin. It is characterised by difficulties with accurate and/or fluent word recognition, and by poor decoding and spelling ability1Elliot, J.G. & Grigorenko, E.L. (2014). The Dyslexia Debate. Cambridge University press..
It is impossible to determine the exact prevalence of dyslexia because of the different ways it can be defined and operationalised. Whilst a large number of children struggle with reading (especially in developing countries), a strict estimate of dyslexia prevalence varies from 4%–5% of the population. However, it is important to understand that dyslexia does not have clear-cut boundaries. Rather, it is a dimensional disorder varying from mild to severe. Therefore, it could be said that dyslexia is simply the lower end of the continuum of reading skills2Protopapas, A. (2019). Evolving concepts of dyslexia and their implications for research and Remediation. Frontiers in Psychology, 10, Article 2873..
Reading disability typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of appropriate classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.
In recent years, many researchers have suggested that reading disability could provide a more neutral and useful concept for describing children who struggle with reading. In eTALE, we often use the term reading disability instead of dyslexia; however, both are defined as a persistent and unexpected difficulty in developing age- and experience-appropriate word reading skills3Elliot, J.G. & Grigorenko, E.L. (2014). The Dyslexia Debate. Cambridge University press..