Wednesday, July 01, 2009

Differentiation of cognitive abilites across the lifespan: WJ III norm analysis "in press"

The following manuscript, which analyzed the WJ III norm data [conflict of interest--I'm a coauthor of the WJ III), has been accepted for publication in the journal Developmental Psychology

Differentiation of Cognitive Abilities across the Lifespan. Elliot M. Tucker-Drob, Department of Psychology University of Virginia Charlottesville, V.A.

Existing representations of cognitive ability structure are exclusively based on linear patterns of interrelations. However, a number of developmental and cognitive theories predict that abilities are differentially related across ages (age differentiation-dedifferentiation) and across levels of functioning (ability differentiation). Nonlinear factor analytic models were applied to multivariate cognitive ability data from 6,273 individuals, ages 4 to 101 years, who were selected to be nationally representative of the United States population. Results consistently supported ability differentiation, but were less clear with respect to age differentiation-dedifferentiation. Little evidence for age modification of ability differentiation was found. These findings are particularly informative about the nature of individual differences in cognition, and the developmental course of cognitive ability level and structure.

Author Summary
In summary, nonlinear factor analytic models were applied to carefully scaled data on seven well-established cognitive abilities measured in a large nationally representative lifespan sample of individuals. Consistent with the ability differentiation hypothesis, results indicated that a general factor accounted for a decreasing amount of (and proportion of) individual differences in the abilities at higher ability levels, suggesting that at higher ability levels more specific cognitive mechanisms may be less constrained and more prominently expressed. However, results were inconsistent with the age differentiation-dedifferentiation hypotheses that the magnitudes of ability relations decrease with childhood age and increase with adult age. There was rather some evidence to suggest that abilities become more related with childhood age, and less related with adult age. It is proposed that future examinations of age differentiation dedifferentiation focus on the multivariate relations among individual differences in rates of longitudinal changes.

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