During the last two or three decades, growing resources have been invested in large-scale research projects on adult development and aging (for overviews, see Deeg, 1989; Migdal, Abeles & Sherrod, 1981; Schaie, 1983; Thomae, 1987). This research has documented the broad range and variability of developmental patterns in middle and later adulthood, but it still gives only a fragmentary picture of the underlying dynamics of developmental change in middle and later adulthood. Recent claims emphasizing modifyability, contextual specifity, lack of connectivity and discontinuity of development (cf. Gergen, 1980; Brim & Kagan, 1980) may be seen not only as propositions about the fundamental nature of development but also as symptoms of theoretical perplexity. It is true that simplistic notions of stability and ordered change in adult development are largely discredited by the bulk of evidence. Nevertheless, we should be aware that difficulties in rinding order and coherence may result from theoretical deficiencies rather than reflect a fundamental feature of development itself.

Related to these points, it has to be noted that, even with the most refined longitudinal or sequential designs we do not capture developmental laws, but, at best, regularities in need of theoretical explanation. Developmental researchers should not be content with simply documenting patterns of continuity and change, but inquire more deeply into the regulative processes and generative mechanisms on historical, social, personal as well as physical or biological levels that bring about, maintain, or forestall continuity and change across the life span (cf. Baltes, 1987; Dannefer & Perlmutter, 1990).