Adaptation of Double-Deficit Hypothesis to Reading Difficulty in Japanese-Speaking Children

Abstract

Wolf and Bowers (1999) proposed the double-deficit hypothesis of developmental dyslexia in which, in addition to phonological deficit, they put forward naming speed deficit as a second core factor of developmental dyslexia. They also reported the double deficit group showing both phonological and naming speed deficits manifested in the most severe reading difficulty. In this study, we investigated the adaptation of the double-deficit hypothesis to 94 Japanese third grade children attending public school. For the sake of comparisons with foreign studies, we used the same criteria as Sunseth and Bowers (2002) for English speakers and the same as Wimmer et al (2000) for German-speaking third graders. The results indicated that, for both sets of criteria, Japanese-speaking children can be classified into three subgroups based on the double-deficit hypothesis. However, the double deficit group was not the most severe group in all tasks. Our findings suggest that the double-deficit hypothesis applies only partly in the case of Japanese third grade children.