“…Considerable evidence has been accumulated on the dependency of developmental changes on the original level of functioning (Berkowitz & Green, 1965;Birren & Morrison, 1961;Granick & Friedman, 1967;Miles & Miles, 1932;Riegel, 1968;Schaie & Strother, 1968;Vernon, 1947), indicating a better maintenance of performance for subjects with superior abilities. Below average or inferior subjects, on the other hand, have often been found to show slower growth, lower peak performances, and more rapid deterioration during later years of life (Bailer, Charles, & Miller, 1967;Kaplan, 1943Kaplan, , 1956Kaplan, Rambaugh, Mitchell, & Thomas, 1963;Muench, 1944; counterevidence by Bell & Zubeck, 1960).…”