Localizing age-related individual differences in a hierarchical structure.

Data from 33 separate studies were combined to create an aggregate data set consisting of 16 cognitive variables and 6832 different individuals who ranged between 18 and 95 years of age. Analyses were conducted to determine where in a hierarchical structure of cognitive abilities individual differences associated with age, gender, education, and self-reported health could be localized. The results indicated that each type of individual difference characteristic exhibited a different pattern of influences within the hierarchical structure, and that aging was associated with four statistically distinct influences; negative influences on a second-order common factor and on first-order speed and memory factors, and a positive influence on a first-order vocabulary factor.