“…The rationales for manipulative research, of course, are too numerous to be discussed at length in the present chapter. The scarcity of manipulative experiments in behavioral gerontology, however, warrants some comments, especially since a variety of recent papers (e.g., Baer, 1970, in press;Baltes & Goulet, 1971;Baltes & Nesselroade, in press;Biren, 1970;Goulet, 1970;Wohlwill, 1970aWohlwill, , 1970c have addressed themselves to formulating strategies aimed at explicating age functions by systematic intervention research. The major tenet underlying the use of manipulative experimentation is that, once developmental functions have been described, research should concentrate on identifying key antecedents and processes by strategies which explicitly involve alterations and modifications of the developmental functions considered.…”