Social norms shape behavior by creating shared expectations about what people typically do and what they approve or disapprove of. Social norms operate through observable patterns and through perceived social approval; they are learned from peers, institutions, and cultural narratives and guide decisions when formal rules are absent or costly to enforce. The philosopher and social scientist Cristina Bicchieri at the University of Pennsylvania frames norms as conditional on two kinds of expectations: empirical expectations about what others do and normative expectations about what others think one ought to do. When both align, norms become powerful motivators of behavior.
Mechanisms of influence
Several psychological mechanisms translate norms into action. Conformity occurs when individuals change their judgments or behaviors to match a group standard, often to avoid social sanctions or to gain acceptance. Classic laboratory evidence comes from Solomon E. Asch at Swarthmore College, who showed that many people altered simple perceptual judgments to match unanimous group responses; on average participants conformed on 32 percent of critical trials, and a large majority yielded at least once. Obedience to authority is related but distinct: people comply when a perceived legitimate authority legitimizes a norm. Stanley Milgram at Yale University found that a substantial proportion of participants followed experimenter commands to administer progressively higher electric shocks to another person, with 65 percent of subjects in the baseline study continuing to the highest voltage. These experiments illustrate how norms endorsed by a majority or an authority can override private preferences and moral hesitation.
Relevance, causes, and consequences
Norms emerge from repeated interaction, uncertainty about appropriate behavior, and the need to coordinate. Descriptive norms describe what is commonly done, while injunctive norms indicate what is socially approved; persuasive communication that leverages these distinctions can change behavior. Robert Cialdini at Arizona State University has documented how norm-based messages -- for example, emphasizing that most people conserve energy -- increase compliance more effectively than abstract appeals to duty. The causal pathway typically involves perception of others’ behavior, anticipation of social rewards or punishments, and internalization when repeated exposure makes the behavior part of one’s identity.
Consequences span individual, social, and environmental domains. Norms can sustain cooperation and public goods provision, enabling collective action where formal institutions are weak. Conversely, harmful norms can entrench discrimination, risky health behaviors, or environmental degradation. Cultural and territorial nuance matters: a practice that is normative in one community may be deviant in another, and tight-knit societies often enforce norms more strongly than looser ones. Norm change is therefore both psychological and sociocultural; it requires shifting expectations across networks and authorities.
Legal, educational, and communications strategies that respect local meanings and credible messengers tend to be more effective. Interventions grounded in evidence about how norms operate — exemplified by the theoretical work of Cristina Bicchieri at the University of Pennsylvania and empirical research by researchers such as Stanley Milgram at Yale University and Robert Cialdini at Arizona State University — highlight that changing what people expect of others is often the most direct route to changing what people do.