Jean Piaget (1896-1980) was a Swiss psychologist and developmental theorist, whose theories of cognitive development have been central to developmental psychology for decades. Piaget is one of the forefathers of constructivist theory, and described himself as a genetic epistemologist, highlighting his interest in the qualitative development of knowledge. He also examined aspects of moral development. Interestingly, Piaget based much of his theory on the observation of his own children.