Individual differences in trajectory of intellectual development over 45 years of adulthood

The hypothesis that individual differences in adult intellectual developmen t reflect variation in life context and personality was examined in 132 Wor ld War IH (WWII) veterans. Intelligence data from the Canadian Army M Test were available for 3 occasions, WWII, 1984-1986 (Int85), and 1989-1991 (Int 90). Performance declined over the 45 years on 5 subtests but improved on t he 6th, Vocabulary. Correlations between WWII and Int90 scores showed consi derable stability of individual differences in intelligence over 45 years. Younger age predicted less decline over 45 years on all subtests; a more en gaged lifestyle predicted less decline on most subtests, and better health and greater introversion predicted less decline on some subtests. Predictor s of change since Int85 were similar to those for the whole period. Implica tions for theories of adult intellectual development are discussed.