Life-Span Development

Another main theme of life span developmental theory is the idea that aging is continuously and simultaneously influenced by a wide range of dynamic biological and social processes. Although it seems trivial to point out that aging has multiple causes, most theories of aging emphasize the nonmalleable aspects of aging. From a life span perspective, it is recognized that some of the antecedents of aging are universal and species-determined, and that some are idiosyncratic or cohort-specific, culture-specific, or specific to a segment of historical time. Further, some of the biogenetic and sociocultural aspects of development and aging are gender-specific, and some of the biological and social aspects of development and aging are gender-invariant. Some of the environmental influences on aging are or seem entirely unique to individuals.

It seems that life span researchers also find it useful to look for conceptual linkages across disciplines. Occasionally, such linkages lead to major advances in how we think about aging processes. Significant advances in the study of aging often reflect multidisciplinary integrations of ideas. For example, recent work in the area of developmental behavioral genetics goes beyond the standard position on organism-environment interaction by calling attention to nonadditive synergistic effects. That is, there are unique combinations of nature and nurture that produce synergistic or optimal outcomes for development. As an example of a synergistic interaction between environmental conditions and heritability, it has been reported that there is a significant increase in the heights of second-generation Japanese persons raised in the United States compared with second-generation Japanese persons raised in Japan. Second-generation Japanese persons raised in the United States were over five inches taller than the American-reared sons of short Japanese fathers and the Japan-reared sons of tall Japanese fathers (see Bronfenbrenner and Ceci).

In conclusion, life span developmental theory provides a basis for describing both gains and losses associated with aging. From a life span developmental perspective, researchers tend to consider the potentials as well as limits of intra-individual change across the life span. Due to a combination of influences, many developmental outcomes are possible for each person, some outcomes are more likely than others, some outcomes can be made more likely, and some outcomes are not possible. From a life span orientation, the understanding of specific aspects of human aging are best understood in a larger context that encompasses the influences of biological and sociocultural factors across time and age.