Domain-specific knowledge as the "Dark matter" of adult intelligence: Gf/Gc, personality and interest correlates

An enduring controversy in intelligence theory and assessment, the argument that middle-aged adults are, on average, Less intelligent than young adult s, is addressed in this study. A sample of 228 educated adults between ages 21 and 62 years was given an array of tests that focused on a broad assess ment of intelligence-as-know ledge, traditional estimates of fluid intellig ence (Gf) and crystallized intelligence (Gc), personality, and interests. T he results indicate that middle-aged adults are more knowledgeable in many domains, compared with younger adults. A coherent pattern of ability, perso nality, and interest relations is found. The results are consistent with a developmental perspective of intelligence that includes both traditional ab ility and non-ability determinants of intelligence during adulthood. A reas sessment of the nature of intelligence in adulthood is provided, in the con text of a lifelong learning and investment model, called PPIK, for intellig ence-as-Process, Personality, Interests, and intelligence-as-knowledge (Ack erman, 1996).