The locus of adult intelligence: Knowledge, abilities, and nonability traits

Some intelligence theorists (e.g., R. B. Cattell, 1943; D. O. Hebb, 1942) have suggested that knowledge is one aspect of human intelligence that is well preserved or increases during adult development. Very little is known about knowledge structures across different domains or about how individual differences in knowledge relate to other traits. Twenty academic and technology-oriented tests were administered to 135 middle-aged adults. In comparison with younger college students, the middle-aged adults knew more about nearly all of the various knowledge domains. Knowledge was partly predicted by general intelligence: by crystallized abilities, and by personality, interest, and self-concept. Implications of this work are discussed in the context of a developmental theory that focuses on the acquisition and maintenance of intelligence-as-knowledge, as well as the role of knowledge for predicting the vocational and avocational task performance of adults.