This chapter explores three primary issues. First, it will consider how theories addressing the etiology of dyslexia have changed over time. Next, it will examine current theories regarding what causes dyslexia. Finally, the chapter concludes with a review of empirical investigations addressing the genetic, neurobiological, and environmental causes of dyslexia.
Changes in Perspective of the Etiology of Dyslexia
As discussed in Chap. 1, the original conceptualizations (originally termed “word blindness”) viewed dyslexia as being caused primarily by a vision or a visual processing problem. It was not until Liberman, Shankweiler, Orlando, Harris, and Bell-Beitz’s (1971) research on Orton’s (1928) classic “symptoms” of dyslexia, b and d reversals, and reading words backward that linguistic processes were considered most important. Liberman et al. found that Orton’s classic symptoms were actually much more a normal developmental variation rather than a set of specific symptoms or predictors...