CONSTRAINTS ON THEORIES OF COGNITIVE AGING

There is currently little consensus regarding what must be explained b y theories of cognitive aging. In the present article, four empirical generalizations that seem to imply certain constraints in theorizing a re identified. These generalizations, and their possible implications or constraints, are that (1) age-related differences are found in a wi de range of cognitive variables, implying that either a large number o f specific factors or a small number of general factors must be contri buting to the age-related differences; (2) the age-related influences on different cognitive variables are not independent, and unique age-r elated influences appear to be few in number and small in magnitude, i mplying that some fairly general factors need to be postulated to acco unt for the shared age-related influences; (3) only a small proportion of distinct age-related variance occurs late in practice and at long presentation durations, implying that adequate explanations must inclu de factors operating when the individuals are just beginning to perfor m the task and when the stimuli can first be registered; and (4) measu res of how quickly very simple cognitive tasks can be performed share considerable age-related variance with many cognitive variables, imply ing that factors related to simple processing efficiency need to be in corporated into the explanations.