Cognitive mechanisms in number processing and calculation: evidence from dyscalculia.

This article presents a framework for the cognitive analysis of number processing and calculation. Within this framework the primary objective is the development of a model that is sufficiently detailed to serve as a basis for explaining the number-processing/calculation performance of both normal and cognitively impaired subjects. First a general model of the cognitive mechanisms for number processing and calculation is outlined. It is shown that patterns of impairments observed in brain-damaged patients support the major assumptions of the model and that the model provides a theoretically motivated framework for interpreting the deficits. A single case is then discussed in some detail, to demonstrate that through detailed analyses of impaired performance the preliminary model can be elaborated to specify not only the general architecture of the number-processing and calculation systems, but also the inner workings of specific components and the consequences of damage to these components. The article concludes with a discussion of several general issues arising from the presented arguments.