One of the commonest complaints of older people is that their memory is not what it used to be. The validity of such subjective reports is borne out by the scientific literature: Memory performance does decline as a function of the normal aging process in healthy adults, although the decline is much more evident with some materials and tasks than it is with others. This variability has given researchers useful clues to the specific memory components or processes that are particularly vulnerable to the effects of aging. Some of this work is described below.

Nearly all the studies described use the cross-sectional method of age comparison; that is, a group of young adults (often college students in their early twenties) is compared with a group of older adults (usually community-dwelling volunteers in their sixties and seventies). Additionally, some studies incorporate...