18 - Developmental dyslexia

Summary

Research on developmental dyslexia seems to have been hampered because the very entity of dyslexia is elusive. A typical and traditional definition, “a profound reading difficulty which is not commensurate with the child's intelligence, and which occurs in spite of adequate schooling” (Stuart-Hamilton 1995: 35), should be taken as tentative. In this chapter, we consider what dyslexia looks like and what problems exist in Japan by discussing the two oft-asked questions concerning correlates of dyslexia and the interaction between dyslexia and script. Although studies on dyslexia in Japanese are surprisingly few compared with those in English, problems involving probable dyslexic children in Japanese are psychologically real and need to be discussed from a wider perspective.

Correlates of dyslexia

Frith (1999:192) defines dyslexia as “a neuro-developmental disorder with biological origin and behavioural signs which extend far beyond problems with written language.” Given this definition, we expect characteristic behavioral and neurological signs of dyslexia to emerge regardless of what language the child may speak if he/she is dyslexic. Indeed, research has shown a variety of correlates of dyslexia which may roughly be classified into five categories: phonological, visual, motoric, temporal processing, and environmental deficits (e.g. Harbib, 2000).

Phonological and phonology-related deficits

In the rubric of a phonological deficit, a wide range of phonological impairments has been identified including poor performance on phoneme segmentation and other tasks (e.g. Lyon, 1995). For example, English-speaking dyslexic children experience great difficulty segmenting cat into three phonemes.