Lexical retrieval in spelling

This thesis is an investigation of how written words are processed and represented for output. A single case study of an acquired dysgraphic patient is presented who produced a serial position effect in spelling tasks characterised by an increase in error rate from word beginning of word end. This pattern is assumed to reflect a deficit in the retrieval of stored orthographic representations. It is suggested that the order of output of letters may be encoded by an ordering of activation values. The nature of the deficit in terms of distinctions between input and output and access and storage are considered. The findings are discussed in relation to an existing connectionist model of spelling which was implemented and lesioned in an attempt to reproduce certain aspects of the patients data. Furthermore, a detailed analysis of the patients spelling errors suggests that orthographic representations consist of representational units other than the single letter and whole word. Finally, the role of the semantic system in lexical retrieval was investigated with regards to the distinction between proper names and common nouns. The ability of two patients to write/read proper names semantically was studied. Differences in the representational properties of proper names may result in them being selectively spared or impaired