Social norms are one of many agents of influence on human behavior. They are widely recognized as an instigator of behavior change, yet their influence goes largely undetected. They have been implicated in antisocial behaviors, such as tax evasion, bystander apathy, and substance abuse. These agents of influence have also been shown to promote prosocial actions, such as environmental protection and healthy eating. They can influence the outcome of political elections, raise the bottom line of corporate profits, and reduce discrimination. The term social norms refers to an individual's beliefs about the common and accepted behavior within a group. Research has consistently shown that communications highlighting the large number of people who engage in a desirable behavior can effectively promote change. This has been shown across a wide range of behaviors, but especially pro-environmental behavior and reducing excessive levels of alcohol consumption. Although the basic influence of social norms has been well established, contemporary research continues to uncover moderators of the effectiveness of this influence. These moderators include the magnetic middle, deviations from the norm, personal values, culture, norm activation, reference to changing frequency, and social identity.