Trait concepts, as well as factor-analytic methodology, arose out of inquiries into the nature of intelligence. Major trait theories can be subsumed under two-factor, multiple-factor, facet, and hierarchical models. Mechanisms of trait formation include experiential contiguity and transfer of training. Our understanding of the nature and organization of traits has been advanced by research in developmental cross-cultural, learning, and cognitive psychology. When redefined in the light of accumulated research findings, intelligence emerges as a useful construct, albeit a more comprehensive and flexible construct that recognizes the modifiability of intelligence and its varied composition as a function of age and cultural context.