Deborah Kelemen explores fundamental questions about the nature of children’s and adults’ concepts and reasoning. How do children conceive of people, animals and objects? How does their reasoning about these domains inter-relate and change over development? Interest in these questions has motivated a wide-range of intersecting projects on the development of teleological, intentional and biological reasoning, agency beliefs, artifact concepts and conventional knowledge. Findings from these studies have clarified debates about the universals of human cognition, the nature of social cognition, moral cognition, conceptual change, social learning and scientific and religious theory-formation. Basic research projects inform a program of applied research on early science education.