Age-related effects on cognition between 20 and 50 years of age

Data from 5391 adults between 20 and 50 years of age were analyzed to determine the magnitude of cross-sectional age-related effects on a set of cognitive variables within this age range, and to examine the degree of independence of age-related influences on different variables. Scores on a test of vocabulary increased about 0.05 standard deviation units per year across this age range, while scores on factors representing memory and space/reasoning decreased about 0.02 standard deviation units per year. Correlational analyses revealed that only small proportions of the age-related effects on different cognitive variables were unique, in the sense that they were independent of the cross-sectional age-related effects on other variables.