Another alternative theoretical explanation for age – related changes in cognitive functioning focuses on why older adults have more problems performing more difficult tasks, or tasks on which they have little practice, simultaneously? Many theorists and researchers believe that with increasing age comes a decline in the amount of available processing resources, the amount of attention one has to apply to a particular situation. The idea of declining pro­cessing resources is appealing, because it would account for poorer performance not only on atten­tion but also on a host of other areas (Salthouse, 1991, 1996).

On the surface the notion of age-related decre­ments in processing resources offers a concise exp­lanation of a wide range of age-related performance differences. But there is a nagging problem about the processing resource construct: It has never been clearly defined (McDowd & Shaw, 2000; Neumann,

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1996; Salthouse, 1991) and is too broad. In fact, although Salthouse (1996) was able to show that some kind of processing resource notion is a par­simonious explanation, the strong version of the resource decline idea that marks much current research has little empirical support. Thus, there have been a number of alternative ways of examin­ing a processing resource hypothesis. Two promi­nent alternative approaches are inhibitory loss and attentional resources.