Morality is a system of beliefs about what is right and good compared to what is wrong or bad. These are principles for how individuals ought to treat one another with respect to justice, others’ welfare, and rights. In order to investigate how individuals understand morality, it is essential to measure their attitudes, beliefs, emotions, and behaviors that contribute to moral understanding. Moral beliefs are related to, but not identical to, moral behavior. It is possible to know the right thing to do but not actually do it. Moral belief is also not the same as knowledge of social conventions, which are arbitrary customs needed for the smooth operation of society.

Moral development focuses on the emergence, change, and understanding of morality over the lifespan. As it pertains to morality, developmentalists study the role of peers and parents in facilitating moral development, the role of conscience and values, socialization and cultural influences, empathy and altruism, and positive development. The interest in morality spans many disciplines (e.g., philosophy, economics, biology, and political science) and specializations within psychology (e.g., social, cognitive, and cultural). Moral developmental psychology research focuses on questions of origins and changes in morality across the lifespan.