Arithmetical ability and disability in turner's syndrome: A cognitive neuropsychological analysis

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Abstract
Children with Turner's syndrome (TS), a sex chromosome abnormality in which the second X chromosome is abnormal or deleted, were given a series of tasks investigating mathematical skill, which were designed to assess the development of components of the model of arithmetic outlined by McCloskey, Caramazza, and Basili (1985), within which number processing skills (reading, writing, transcoding, and comprehending numbers) and calculation skills (including fact retrieval and the implementation of procedures) represent distinct modular components. The results indicated intact number processing skills in TS but an impaired calculation system. Within calculation, speed of retrieval of addition facts was impaired. These results cannot reflect generalized slow responding in TS, given Temple and Carney's (1996) recent finding of rapid rate of responding in TS when reading. Further impairments within the calculation system included enhanced rates of certain error types in the retrieval of multiplication facts. In solving arithmetical problems, participants with TS also made significantly more multiplication and division errors than did controls, and a significantly larger number of their errors had a basis in difficulty with the implementation of procedures. Thus, whereas the arithmetical disorder in TS selectively affects calculation rather than number processing, its effects within the calculation system are multiple. The results are compatible with the findings of Rovet, Szekely, and Hockenberry (1994) of poor procedural skills and poor fact retrieval on a timed task. They also tally with the evidence of Temple, Carney, and Mullarkey (1996) for impairment of components of executive skills in TS.