Working Memory in Perspective

In this chapter we examine the empirical evidence for adult age changes in the components of the Baddeley and Hitch working memory model, and highlight some methodological and theoretical issues raised by the study of age differences in working memory. Baddeley (1996, p. 19) argues that ‘ageing may be an interesting and productive variable to study within the context of working memory’. The idea that adult age changes in the available capacity of working memory underlie deficits in reasoning and language abilities has been extremely influential. However, the majority of work in this area has conceptualised working memory in terms of a general limited-capacity system, rather than using the notion of the Baddeley and Hitch three component model (WM model) with specialised subsystems for the maintenance of verbal and visuo-spatial information.

In the aging literature, the usual view of working memory is that age differences reflect a decrease in the amount of cognitive resources that can be shared out to deal with competing task demands. This maps onto the predominant limited-resource model of working memory in the North American literature. In the current chapter we will not discuss in detail the research that largely utilises this resource capacity approach to working memory, but will instead concentrate on research specifically relevant to the WM model. In the aging literature particularly, this notion of working memory is closely tied in to other conceptions of limitations on information-processing, such as attentional capacity and processing speed (Salthouse, 1991). Salthouse (e.g. 1992) has argued that slowed speed of processing information underlies the decline in capacity of working memory with age. Evidence from statistical partialling techniques suggests that age-related variance in working memory can largely be explained in terms of processing speed at both the beginning and end of the lifespan (Chuah & Maybery, 1999; Kail & Salthouse, 1994; Salthouse, 1992).

The WM model has been utilised less in aging research than limited general resource models. However, the WM model does have promise as a tool for understanding adult aging because it allows the possibility of a functional account of exactly how and why cognitive changes occur with age, rather than the basic assertion that age differences are ‘resource’

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