Introduction
Construing cohesion and coherence in human development over the life span is often seen as coterminous with the search for causal order (see Overton & Reese, 1981). The search for continuous causal chains in development, however, tends to obscure the fact that the conditions constituting the developmental ecology for an individual are to a large extent the results of actions. Human development is, by nature, dependent on culture; observed developmental patterns reflect tendencies of development-related control extant in a given cultural and historical situation. Developmental research, thus, has to investigate not only the causal nexus but also the actional nexus between developmental phenomena. We have to extend the scope of our explanatory schemes to account not only for the causal mechanisms but also for the systems of action that generate developmental changes, and we have to recognize that observed regularities of development usually have the status of quasi laws that are conditional on the execution (or nonexecution) of certain actions and interventions (see Brandtstädter, 1981, 1984).
Cultural formation of development involves, and is partly mediated by, processes of self-regulation. The adult person shapes his or her development by opting for certain life designs, striving toward developmental goals, as well as by selecting and constructing developmental niches that fit personal interests and competences (Lerner & Lerner, 1983; Super & Harkness, 1986). Individuals, however, are not the sole producers of their development. Any effort to optimize personal development over the life span is subject to cultural and natural constraints and usually generates unpredicted and unintended side effects.