<P> He was a founding member of the European Academy of Sciences, a member of the Berlin - Brandenburg Academy of Sciences, and a member and vice-president of the Deutsche Akademie der Naturforscher Leopoldina . Paul Baltes also became a member of the Order Pour le mérite for scientists and artists and a foreign member of the American Academy of Arts and Sciences and the Royal Swedish Academy of Sciences . </P> <P> As to research and theory, Baltes was interested in advancing a life - span view of human ontogenesis that considers behavioral and cognitive functioning from childhood into old age using a family of perspectives that together specify a coherent metatheoretical view on the nature of development . Other substantive topics included work on historical cohort effects, cognitive development, a dual - process conception of lifespan intelligence, and the study of wisdom . His interests also included models of successful development and the cross-cultural comparative study of self - related agency beliefs in the context of child development and school performance . Together with his late wife, Margret Baltes, he proposed a systemic metatheory of ontogeny which characterizes lifespan development as the orchestration of three processes: selection, optimization, and compensation . </P> <P> Baltes was active in various national and international organizations including the US Social Science Research Council (where he served as chair of the Board of Directors from 1996 until 2000), the German - American Academy Council, the Berlin - Brandenburg Academy of Sciences, and the European Academy of Science . Regarding interdisciplinarity, Baltes was engaged primarily in two projects: he chaired (together with Karl Ulrich Mayer) the Berlin Aging Study and, together with the Sociologist Neil Smelser, he was co-editor - in - chief of the 26 - volume International Encyclopedia of the Social and Behavioral Sciences (Elsevier) which appeared in 2001 . </P> <P> Baltes was the author or editor of 18 books and more than 250 scholarly articles and chapters . For his work, he was honored with numerous awards including honorary doctorates and election as foreign member of the American Academy of Arts and Sciences and the Royal Swedish Academy of Sciences, and in 2000 to the German order Pour le mérite of Science and the Arts . </P>

According to research by baltes and associates in which decade is wisdom acquistion most important