The main purpose of this chapter is to discuss external constraints upon individuals' developmental regulation. Such external constraints include biological and sociostructural factors as well as age-normative conceptions commonly shared in a given society. The stage for a discussion of these phenomena is set by developing the conceptual framework of life-span developmental psychology. A more specific discussion of age-related constraints to developmental regulation across the life course follows in terms of a brief sketch of biological-genetic factors, a consideration of the main types of sociostructural influences, and an elaborate discussion of age-normative conceptions. In this chapter, external constraints to developmental regulation are discussed, not only as restrictive factors, but as a functional and indisposable scaffold that provides time-structured opportunities for developmental regulation across the life course.

For the human species the variability of behavior is substantial, both interindividually and intraindividually across life-course changes. This implies greatly enhanced opportunities, but it also brings about the necessity to select from the many options in terms of choosing a particular track and then staying focused on it (see Chapter 1). This selectivity requirement cannot be managed by the individual herself. The task of choosing and maintaining focus on one path from a completely unstructured pool of behavioral options would be overwhelming.