Kohlberg's stages of moral development build upon Piaget's work in this area. Kohlberg proposed 6 stages of moral reasoning grouped into 3 levels - preconventional, conventional, and postconventional. At the preconventional level, reasoning is based on obedience and self-interest. The conventional level focuses on maintaining social norms and relationships. Finally, the postconventional level reasons from a social contract perspective, weighing both individual rights and societal benefit. Kohlberg used moral dilemmas like the Heinz story to assess people's justifications and place them within these 6 stages of increasingly sophisticated moral reasoning.