 From an early age, humans exhibit a tendency to identify, adopt, and enforce the norms of their local communities. Norms are the social rules that mark out what is appropriate, allowed, required, or forbidden in different situations for various community members. These rules are informal in the sense that although they are sometimes represented in formal laws, such as the rule governing which side of the road to drive on, they need not be explicitly codified to effectively influence behavior. There are rules that forbid theft or the breaking of promises, but also rules which govern how close it is appropriate to stand to someone while talking to them, or how loud one should talk during the conversation. Thus understood, norms regulate a wide range of activity. They exhibit cultural variability in their prescriptions and proscriptions, but the presence of norms in general appears to be culturally universal. Some norms exhibit characteristics that are often associated with morality, such as a rule that applies to everyone and prohibits causing unnecessary harm. Other norms apply only to certain people, such as those that delimit appropriate clothing for members of different genders, or those concerning the expectations and responsibilities ascribed to individuals who occupy positions of leadership. The norms that prevail in a community can be more or less fair, reasonable, or impartial, and can be subject to critique and change.