Haruhara, P. N. 1 , Uno, A. 2 , Rankin, Q. 3 & Wydell, T. 4
1 Mejiro University, Japan
2 University of Tsukuba, Japan
3 Royal College of Art, UK
4 Brunel University London, UK
The Hypothesis of Granularity and Transparency (Wydell and Butterworth, 1999) accounted for the dissociation between poor-reading-performance in English and superior-reading-performance in Japanese (syllabic-kana and morphographic-kanji) in an English-Japanese bilingual. His phonological deficit which had led to dyslexia in English as seen in other studies (Ramus, 2003) did not affect his reading of Japanese kana/kanji.
According to this Hypothesis, orthographies can be described in transparency and granularity dimensions with the predictions that phonological dyslexia would be rare in (i) shallow orthographies where print-sound translation is transparent (one-to-one) and in (ii) opaque orthographies where the smallest orthographic unit representing sound is coarse (syllable/word as opposed to phoneme). English has an opaque orthography with inconsistent grapheme-to-phoneme-correspondences.
Thus the Hypothesis also accounted for the difference in the prevalence of dyslexia across different orthographies (10-12% for English; 3-4% for Italian and 0.8-6.9% for Japanese)
We herewith report that some of Japanese-English bilingual postgraduate students in London with recent diagnosis of dyslexia in English exhibited a similar dissociation between the languages, and others showed both phonological and visuo-spatial deficits when tested in Japanese. Yet hitherto none of them had been diagnosed as dyslexic while they were in Japan. We address these issues in the discussion.