Do different orthographies share the same mechanisms of reading? A review of research on and models for Japanese acquired dyslexia

Abstract

Background: The Japanese writing system has two distinctive orthographies: morphographic Kanji and syllabographic Kana. The difference between Kanji and Kana in terms of both character–sound correspondences (i.e., pronunciation predictability) and the character–meaning relationship is quite striking. Research on acquired dyslexia in Japanese means studying “monolingual-bi-scriptal readers” with brain damage, giving us a rare chance to examine whether the identical brain damage has similar or discrepant effects on the processes of reading aloud in different orthographies.Aims: This article mainly reviews cognitive neuropsychological research on Japanese acquired dyslexia and proposed reading models for Japanese, then asks how well existing reading models can explain patterns of impaired oral reading in Japanese.Main Contribution: This review attempts to provide a comprehensive picture of research on Japanese acquired dyslexia, which is still not especially well-known in the English literature and has not even been critically considered in Japan. Such a review may offer a better understanding of dyslexia patterns in bi-scriptal writing system. Theoretical interpretations of Japanese acquired dyslexia using the triangle model and the Dual Route Cascaded (DRC) model developed for English also provide implication about common cognitive procedures for reading across different orthographies.Conclusion: Cognitive neuropsychological studies which used well-manipulated and well-controlled reading stimuli revealed that Japanese patients with acquired dyslexia display effects of the same psycholinguistic variables as those observed in English acquired dyslexic patients and in both Kanji and Kana. This suggests (i) that patterns of Japanese acquired dyslexia are script-nonspecific (i.e., script-independent) and (ii) that the manner in which brain disease/injury disrupts reading processes is probably the same across different orthographies (i.e., a universal basis for acquired dyslexia). Together, these two outcomes imply universal mechanisms underlying oral reading. The triangle model could account for patterns of Japanese acquired dyslexia, whereas the DRC model needed to incorporate additional assumptions. So, certain features of the models and results may favour the former model.