Linguistic and Cognitive Factors of Developmental Dyslexia Across Three Script Types

Abstract

This study examined the interrelationship between linguistic characteristics and individual cognitive factors that contribute to developmental dyslexia among readers of alphabetic systems, Japanese syllabaries, and Chinese morpho-syllabaries. Among alphabetical languages. English has a complex syllable structure and opaque orthography; therefore, literacy acquisition requires particularly precise phonological skills. Deficiencies in phonological skills may lead to developmental dyslexia. The prevalence rate of developmental dyslexia is relatively high among English speakers. Japanese has an orthographically transparent syllabary and a simple syllable structure; therefore, the prevalence rate of hiragana dyslexia is less than 1%. Visuo-orthographic knowledge and morphological and syllabic awareness are required for literacy acquisition in visually complicated Chinese hanji. Children with dyslexia often exhibit deficiencies in these functions. Across the script types, an awareness of the linguistic level represented in each script is essential for literacy acquisition: phonemic awareness for the alphabetic script, syllable awareness for hiragana, and syllable and morphological awareness for hanji. Impaired rapid automatized naming is commonly observed among individuals with developmental dyslexia across all three script types. This impairment is likely because of foundational processing difficulties involved in language-script conversion.