Social norms are shared standards of acceptable behavior by groups. Social norms can both be informal understandings that govern the behavior of members of a society, as well as be codified into rules and laws. Social normative influences or social norms, are deemed to be powerful drivers of human behavioural changes and well organized and incorporated by major theories which explain human behaviour. Institutions are composed of multiple norms. Norms are shared social beliefs about behavior; thus, they are distinct from "ideas", "attitudes", and "values", which can be held privately, and which do not necessarily concern behavior. Norms are contingent on context, social group, and historical circumstances. Scholars distinguish between regulative norms (which constrain behavior), constitutive norms (which shape interests), and prescriptive norms (which prescribe what actors ought to do). The effects of norms can be determined by a logic of appropriateness and logic of consequences; the former entails that actors follow norms because it is socially appropriate, and the latter entails that actors follow norms because of cost-benefit calculations. Three stages have been identified in the life cycle of a norm: (1) Norm emergence – norm entrepreneurs seek to persuade others of the desirability and appropriateness of certain behaviors; (2) Norm cascade – when a norm obtains broad acceptance; and (3) Norm internalization – when a norm acquires a "taken-for-granted" quality. Norms are robust to various degrees: some norms are often violated whereas other norms are so deeply internalized that norm violations are infrequent. Evidence for the existence of norms can be detected in the patterns of behavior within groups, as well as the articulation of norms in group discourse. There are varied definitions of social norms, but there is agreement among scholars that norms are: social and shared among members of a group, related to behaviors and shape decision-making, proscriptive or prescriptive socially acceptable way of living by a group of people in a society.