Constraints on theories of cognitive aging

Abstract

There is currently little consensus regarding what must be explained by theories of cognitive aging. In the present article, four empirical generalizations that seem to imply certain constraints in theorizing are identified. These generalizations, and their possible implications or constraints, are that (1) age-related differences are found in a wide range of cognitive variables, implying that either a large number of specific factors or a small number of general factors must be contributing to the agerelated differences; (2) the age-related influences on different cognitive variables are not independent, and unique age-related influences appear to be few in number and small in magnitude, implying that some fairly general factors need to be postulated to account 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 include factors operating when the individuals are just beginning to perform the task and when the stimuli can first be registered; and (4) measures of how quickly very simple cognitive tasks can be performed share considerable age-related variance with many cognitive variables, implying that factors related to simple processing efficiency need to be incorporated into the explanations.Research concerned with the relations between adult age and cognitive performance has been increasing dramatically over the last several decades. Despite the rapid expansion of research, however, there is still little consensus regarding the reasons for the negative relations that are typically reported between chronological age and the measures of memory, reasoning, and spatial ability sometimes referred to as comprising Type A (Hebb, 1942) or fluid (Horn & Cattell, 1963) cognition. The primary purpose of this article is to describe several sets ofempirical results that appear to place important constraints on theoretical explanations of age-related cognitive decline phenomena.It is helpful to begin by describing the broad phenomenon in need ofexplanation by theories ofcognitive aging. Consider the distribution of scores on a cognitive test, such as immediate free recall of a list of unrelated words. In a recent experiment (Salthouse, 1993b), a total of305 adults between 19 and 84 years of age attempted to remember two 12-word lists (presented auditorily at a rate of 1 word every 2 sec), and their average scores across the two lists ranged from near zero to perfect (top panel of Figure I). Because the sample included people of different ages, the distribution can be disaggregated by age. That is, the individuals can be ordered by their ages, and then the scores plotted by age (as in the bottom panel of Figure 1). This type of disaggregation typically results in considerable variability at each age, but with an average This research was supported by National Institute on Aging Grant R37 AG6826 to T.A.S. I would like to thank three reviewers for their constructive comments on a...

A study of performance on tests from the CANTAB battery sensitive to frontal lobe dysfunction in a large sample of normal volunteers: Implications for theories of executive functioning and cognitive aging

“…According to Salthouse (1985Salthouse ( , 1996 and Nettelbeck and Rabbitt (1992) (Nettelbeck and Rabbit, 1992, p. 191) The first prediction is upheld to some extent, except for the tests of spatial working memory and attentional set shifting. The second is also upheld, as age-related variance was attenuated considerably by partialing out the effects of speed.…”

“…West, 1996). Second, whether any relationship between particular tests of executive function and age can be attributed to general factors, such as informationprocessing speed (Nettelbeck & Rabbitt, 1992;Salthouse, 1985Salthouse, , 1996 or fluid intelligence (Duncan et al, 1995).…”

“…Analysis 1 focused on the interrelationships between the main test variables, age, and an index of speed of information-processing (choice reaction time for matching to sample between two visual stimuli) (Downes et al, 1989;Robbins et al, 1994). This enabled a test of two predictions derived from Salthouse's (1985Salthouse's ( , 1996 theory of cognitive aging (see Nettelbeck & Rabbitt, 1992). We also analyzed the contribution of fluid intelligence (AH 4 2 scores) to the age-related correlations with specific cognitive measures.…”

“…The data could be analyzed within the context of one theory of cognitive aging-that speed of information-processing underlies all age-related declines in cognitive function (Salthouse, 1985(Salthouse, , 1996-by using one set of variables from the CANTAB battery to provide indices of speed of processing (reaction times) (Nettelbeck & Rabbitt, 1992).…”

Age-related differences in auditory event-related potentials during a cued attention task

“…A wide range of cognitive tasks share much of their age-related variance, which suggests that age-related differences are largely due to changes in basic processes that are engaged during many types of cognitive activities (Lindenberger and Baltes, 1994;McDowd and Shaw, 2000;Salthouse, 1996). Inhibitory aspects of attention have been proposed to be a basic component of cognitive aging (Hasher and Zacks, 1988), and are thought to be important for switching attention among relevant events (Hasher and Zacks, 1988;McDowd and Shaw, 2000).…”