Several theories of sequential changes in intellectual functioning during adolescence and adulthood are addressed in this article. Methodological difficulties of testing these theories through longitudinal research are summarized. Educational implications of the Reflective Judgment Theory on research in intellectual development during college…

Intended as a nontechnical review of current scientific knowledge in the field, this essay considers the nature of primary and secondary intellectual abilities, plus the major features of, and the development of individual differences in, the skills and capacities constituting intelligence. Part of a theme issue on intelligence. (Author/SJL)