ABSTRACT
Developmental dyslexia, reading disability, and reading impairment are three interchangeable terms that refer to unexpected poor performance in reading (Wagner, 2005). Expected levels of reading performance can be based on normative data from age-matched peers or based on an individual’s oral language or general cognitive ability. The observed poor reading performance is unexpected in the sense of not being explained either by lack of an opportunity to learn (i.e., ineffective instruction) or by other potential causes including severe intellectual deficits, language impairments, or impaired basic sensory capacities such as blindness. Developmental dyslexia is distinguished from acquired dyslexia, with acquired dyslexia referring to impaired reading in formerly normal readers due to brain injury or illness. Our focus in the present chapter will necessarily be limited to developmental as opposed to acquired dyslexia. We begin by considering the role of single-word reading in identifying individuals with dyslexia, and then review attempts to classify individuals with dyslexia into subtypes on the basis of their pattern of performance at single-word reading as a function of the kind of stimuli that are read.
