Developmental Psychology

There has been a long-standing debate in the psychological literature about what aspects of change define development and whether or not development occurs across the life span or only in early life (for reviews see Bengtson and Schaie; Cairns; Valsiner). Traditionally, developmental psychology focused primarily on the description and explanation of positive changes (e.g., increased adaptive capacity or growth) in the structure and function of mind and behavior. Change, within this tradition, is considered to reflect development if one or more of the following criteria are met: (1) it is directed toward a state of maturity; (2) it is quantitative and qualitative (stagelike) in nature; (3) it is relatively robust or irreversible; and/or (4) it moves toward greater complexity and differentiation. Using these criteria to define development encourages theoretical precision but also restricts the concept primarily to growth in early life. Is change observed during adulthood and old age associated with development or with processes of aging?

The life-span approach outlined by Paul B. Baltes (1997; Baltes, et al.) proposes that development is not completed at young adulthood (maturity) but extends across the entire life course. Each age period (e.g., infancy, adolescence, adulthood, old age) has its own developmental tasks. When viewed together, however, these age-specific phenomena contribute to continuous (cumulative) and discontinuous (innovative) change throughout life. The great regularity of development observed in infancy and childhood may be attributed to the fact that the biological and cultural influences that shape childhood are more programmed (genetically and societally) than is true for late adulthood. In old age, the conjoint dynamics of biological and cultural influences are less well-orchestrated, in part because the culture of old age is still evolving.

The life-span approach of Baltes and colleagues alerts researchers to the fact that development can be multidirectional in that it involves trajectories of positive growth, stability, and negative change (loss) across the life span. A classic example of this concept is longitudinal research on the trajectories of fluid versus crystallized intelligence during adulthood and into old age (e.g., Schaie). Dimensions of fluid intelligence (e.g., spatial ability, reasoning, perceptual speed) generally show decline beginning in middle age, whereas aspects of crystallized intelligence (e.g., knowledge) remain relatively stable up to at least age eighty.

Expanding the concept of development from a growth model to a multidirectional model led to the insight that development is likely always a combination of gains and losses. A gain in one direction, for example, may exclude alternative pathways of development. The search for gains and losses across the life span has led to much recent research on the plasticity of mind and behavior; the fundamental role of processes of selection, optimization, and compensation in development; and profiles of successful aging.