Cognitive dedifferentiation with increasing age and proximity of death: Within-person evidence from the Seattle Longitudinal Study.

A central aim of life-span psychology is to understand ontogenetic changes in the structure of individuals' actions, thoughts, and behaviors. The dedifferentiation hypothesis of cognitive aging suggests that the structure of individuals' cognitive abilities becomes less differentiated in old age. Empirical tests have almost exclusively approached this hypothesis from a between-person difference perspective and produced a mixed set of findings....