Case studies in working memory: a case for single cases?

Patterns of cognitive deficit in single neuropsychological cases are common sources of evidence for theories of normal cognition. In particular, the working memory model has benefited from data obtained from a number of contrasting patients, in some cases resulting in modifications of the working memory model. In this paper, patterns of data from short-term memory patients and anarthric patients are compared with patterns of data from normal subjects. The patterns of patient data that were unlike those patterns typically found for groups of normal subjects, could be incorporated within a modified version of the articulatory loop component of the working memory model. However a small number of individual normal subjects also did not show the pattern that is reported on the basis of average performance of groups of normal subjects. This causes some difficulty in interpreting those data from such 'aberrant normal' patterns, and those data from single patients with functional cognitive deficits. The implications of these findings for the interpretation of neuropsychological data are discussed in the context of the working memory model, but with the intention of making a general point pertaining to the development of functional models of cognition. It is argued that single case studies should continue to provide a useful source of evidence, providing that care is exercised in considering the implications of such data for models of normal cognition.