Bilingual Biscriptal Deep Dyslexia

Abstract

Studies of deep dyslexia in Japanese patients, and of non-word reading by deep dyslexic readers of alphabetic scripts, suggest a general principle that reading that depends on the mapping of characters onto phonological segments (phonemes in the case of alphabetic scripts, syllables in the case of syllabaries) is impossible in deep dyslexia. We describe a case of deep dyslexia in a patient who premorbidly could read English and Nepalese. As the latter is written in the syllabic Devanagari script, this case may be used to explore the generality of this principle. It would be expected that reading Nepalese words written in the syllabic script would be more difficult than reading English words written in the Roman alphabet. In oral reading tasks this was the case, even though Nepalese was the patient's first language. However, further studies showed that he could understand Nepalese words written in the syllabic script at least as well as English words written in the Roman alphabet, and that he could read aloud Nepalese words written in the Devanagari script, provided he was allowed to respond in English. In addition, naming of pictures was much worse in Nepalese than in English. Therefore this patient's difficulties in reading Nepalese aloud were output difficulties, not difficulties in reading a syllabic script. We argue that the superiority of expressive speech in English over expressive speech in Nepalese arose because the patient had had intensive speech therapy in English and no speech therapy in Nepalese. We also conclude that his reading performance demonstrates that the reading of syllabic scripts is not necessarily abolished in deep dyslexia. The inability of Japanese deep dyslexics to read aloud or comprehend the syllabic script kana is thus not simply a function of this script being a syllabary. This inability therefore remains to be explained.