Pertinent Theories

Several theories have been advanced concerning the attenuation of cognitive decline in aging, with two theories receiving perhaps the most attention: Salthouse's (1991) "disuse" theory and Schooler's (1987) environmental complexity hypothesis. The disuse theory posits that the changing activity patterns that accompany the aging process lead to disuse and subsequent atrophy of the skills needed to perform some cognitive activities, for example, information-processing speed (Salthouse, 1996). Support for this theory has come from cognitive training research that has been interpreted as evidence that the decline in Gf can be reversed. Elderly people can be trained to improve their fluid and spatial skills, such as the ones measured by the PMA Space and Reasoning subtests (Baltes & Willis, 1982; Schaie, 1996; Schaie & Willis, 1986), and they can be trained to improve their episodic memory (Kliegl, Smith, & Baltes, 1990; Verhaeghen, 1993).

Reviews of the bulk of literature in this area show that even minor interventions can lead to significant performance gains (Labouvie-Vief, 1985). The results are interesting, and do, indeed, suggest the need for an educational psychology of the older adult learner (Willis, 1985). Whether the ability to reverse a decline casts "grave doubts" on the "irreversible decrement models that assume normative patterns of intellectual decline" (Schaie & Willis, 1986, p. 224) is another matter. We don't believe that norms make any such assumption of irreversibility. They describe what is, not what might be under different circumstances. Fluid intelligence implies the ability to solve new problems in adaptive, flexible ways. Once training intervenes, these problems are no longer new. Transfer of training has been supported (Baltes & Willis, 1982), but such studies neither imply a universal gain in fluid intelligence nor do they offer meaningful support to Salthouse's (1991) disuse theory. Further, young adults also show improvement when trained on fluid ability tasks (Denney, 1982), and the results of "studies in which elderly adults have been compared with younger adults [indicate] that there is a decrease in plasticity with increasing age" (p. 817, italics ours). The key question is whether individuals who are trained on tasks like the PMA fluid subtests will improve substantially on the WAIS-III P-IQ or POI six months after the training (controlling for a Wechsler practice effect). We doubt it, but that is the type of research result that would make us share the optimism of investigators like Schaie and Willis (1986) regarding the importance of the training studies and make us reconsider the possible validity of Salthouse's disuse theory.

Schooler's (1987) theoretical approach to maintenance of intelligence concerns the complexity of a person's environment. More complex environments comprise diverse stimuli and re quire complex decisions; complex activities that take place in such environments will enhance and maintain related cognitive skills, in contrast to activities that do not place significant demands on a person's cognitive skills. The theory predicts that elderly adults who participate regularly in demanding activities will maintain their intellect more so than those who do not, perhaps forestalling or attenuating the inevitable decline. This prediction, however, is also consistent with the underlying concepts of Salthouse's disuse theory. The research summarized briefly in the next section addresses the relationship of active engagement in cognitive activities to maintenance of cognitive ability in old age.

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