A case study of an English-Japanese bilingual with monolingual dyslexia Taeko Nakayama Wydell a, *, Brian Butterworth b a Department of Human Sciences, Brunel University, Uxbridge, Middlesex UB8 3PH, UK b University College London, Gower Street, London WC1E 6BT, UK Received 28 April 1998; accepted 19 February 1999 Abstract We report the case of AS, a 16 year-old English/Japanese bilingual boy, whose reading/ writing difficulties are confined to English only. AS was born in Japan to a highly literate Australian father and English mother, and goes to a Japanese selective senior high school in Japan. His spoken language at home is English. AS’s reading in logographic Japanese Kanji and syllabic Kana is equivalent to that of Japanese undergraduates or graduates. In contrast, his performance in various reading and writing tests in English as well as tasks involving phonological processing was very poor, even when compared to his Japanese contemporaries. Yet he has no problem with letter names or letter sounds, and his phoneme categorisation is well within the normal range of English native speakers. In order to account for our data that show a clear dissociation between AS’s ability to read English and Japanese, we put forward the ‘hypothesis of granularity and transparency’. It is postulated that any language where orthography-to-phonology mapping is transparent, or even opaque, or any language whose orthographic unit representing sound is coarse (i.e. at a whole character or word level) should not produce a high incidence of developmental phonological dyslexia.  1999 Elsevier Science B.V. All rights reserved. Keywords: Dyslexia; Phonological impairment; Hypothesis of granularity and transparency; Kanji and Kana 1. Introduction We describe for the first time a bilingual and biscriptal boy who is severely 0010-0277/99/$ - see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0010-0277(99)00016-5 COGNITION Cognition 70 (1999) 273–305 * Corresponding author. Tel.: +44-1895-274000 Ext. 3452; fax: +44-1895-237573; e-mail: taeko.wydell@brunel.ac.uk