Application of the Double Deficit Hypothesis to Two Japanese Writing Systems

: The double deficit hypothesis (DDH) classifies children into three deficit groups: the phonological awareness deficit (PAD) group, naming speed deficit (NSD) group, and double deficit (DD) group. The DD group shows the most severe reading difficulty according to the DDH. However, there are several reports showing that the DD group did not manifest the most severe reading difficulty. Troppa et al. (2002) postulated one of the reasons for this discrepancy presented in previous reports was different writing systems. In our study, we classified Japanese-speaking children into three deficit groups based on the DDH and investigated whether the DD group manifested the most severe difficulty in reading Hiragana and Kanji, separately. The participants were 795 Japanese-speaking children from grades 1 to 6. Based on the results of a reading attainment test, we classified them, respectively, into Hiragana difficult reading and Kanji difficult reading groups. Results showed that the DD group within the Hiragana difficult reading group did not show the most severe reading difficulty, while the DD group within the Kanji difficult reading group manifested the most severe reading difficulty. This outcome suggests that the severity of the DD group may be affected by differences in writing systems.