Lexical decision performance in developmental surface dysgraphia: Evidence for a unitary orthographic system that is used in both reading and spelling.

The relationship between spelling, written word recognition, and picture naming is investigated in a study of seven bilingual adults who have developmental surface dysgraphia in both Greek (their first language) and English (their second language). Four of the cases also performed poorly at orthographic lexical decision in both languages. This finding is consistent with similar results in Italian that have been taken as evidence of a developmental impairment to a single orthographic system that is used for both reading and spelling. The remaining three participants performed well at orthographic lexical decision. At first sight, preserved lexical decision in surface dysgraphia is less easy to explain in terms of a shared orthographic system. However, the results of subsequent experiments showed clear parallels between the nature of the reading and spelling difficulties that these three individuals experienced, consistent with the existence of a single orthographic system. The different patterns that were observed were consistent with the claims of Friedmann and Lukov (2008. Developmental surface dyslexias. Cortex, 44, 1146-1160) that several distinct sub-types of developmental surface dyslexia exist. We show that individual differences in spelling in surface dysgraphia are also consistent with these sub-types; there are different developmental deficits that can give rise, in an individual, to a combination of surface dyslexia and dysgraphia. Finally, we compare the theoretical framework used by Friedmann and her colleagues that is based upon the architecture of the DRC model with an account that relies instead upon the Triangle model of reading].