Recent work on adult thought has focused on the emergence of relativistic, dialectic, or integrative assumptions about knowledge. In 1981, Kitchener and King developed a model of reflective judgment that describes seven sets of assumptions about reality and knowledge and corresponding concepts of intellectual justification. This article reports a 2-year longitudinal study of three groups of adolescents and young adults (n = 59) who were tested on the Reflective Judgment Interview and on the Concept Mastery Test, a measure of verbal aptitude. Significant group (p