ABSTRACT
Numerous large-scale, cross-sectional and longitudinal investigations have helped to characterize the basic nature of age differences and age changes in cognitive functioning across much of the adult lifespan. We know, for example, that average cognitive test performance declines in adulthood, although the specific age when decline first emerges varies across abilities and in some cases may occur earlier than previously appreciated (Salthouse, 2004). We also know that the timing and rate of decline vary markedly across individuals (Salthouse & Ferrer-Caja, 2003). Although the target of considerable research, the origins of individual differences in the aging of cognitive abilities remain largely unknown (Anstey & Christensen, 2000). In the search for the sources of individual differences in cognitive aging, some researchers emphasize the importance of neurobiological processes (Hedden & Gabrieli, 2005), while others emphasize the importance of psychosocial factors (Pushkar, Etezadi, Andres, Arbuckle, Schwartzman, & Chaikelson, 1999). Although these two approaches are distinct, they need not be incompatible as late-life cognitive functioning is likely the result of a complex interplay between neurobiological changes and psychosocial adaptations (Baltes & Baltes, 1990).
