Global and Domain-Specific Longitudinal Changes in Cognition throughout Adulthood

Normative adult age-related decrements are well documented for multiple domains of cognitive functioning (e.g. Episodic Memory, Processing Speed, Fluid Reasoning, Spatial Visualization). However, it is currently unclear whether these decrements each reflect a distinct and independent developmental phenomenon, or (in part) a more global phenomenon. Recently, a handful of studies have been published indicating moderate to large magnitudes of positive relations among individual differences in rates of changes in different domains of cognitive functioning. This suggests that a small number of dimensions, or even a single dimension, may underlie aging-related deficits in these different domains. This possibility was directly examined using multivariate cognitive ability data from 3,560 adults 18-97 years of age, 1,281 of whom returned for a second assessment up to 7 years later. A combination of latent difference score models and growth curve models was applied to examine the dimensionality of individual differences in longitudinal changes. A hierarchical structure of maturational changes emerged, with approximately 500f the change occurring in each cognitive domain attributable to global (domain-general) processes. Although it is generally assumed that systematic and pervasive sources of maturational decline only emerge in later adulthood, this same general pattern held for younger (ages 18-50 years) as well as older (ages 51-97 years) adults.

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