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Peer pressure is an influence when a peer group, or individual encourages another person to change their values, or behaviors to suit other peoples convenience. This includes membership groups, in which individuals are "formally" members (such as political parties and trade unions), or social cliques in which membership is not clearly defined. They may also recognize dissociative groups with which they would not wish to associate, and thus they behave adversely, in ways concerning that group's behaviors. In general, peer pressure is a form of social pressure by a group upon an individual who must take action in order to be accepted.
Peers become an important influence on behaviour during adolescence, and peer pressure has been called a hallmark of an adolescent experience. Peer conformity in young people is most pronounced with respect to style, taste, appearance, ideology, and values. Peer pressure is commonly associated with episodes of adolescent risk taking (such as delinquency, drug abuse, sexual behaviours, and reckless driving) because these activities commonly occur in the company of peers. Affiliation with friends who engage in risk behaviors has been shown to be a strong predictor of an adolescent's own behavior. Peer pressure can also have positive effects when youth are pressured by their peers toward positive behaviour, such as volunteering for charity  or excelling in academics. The importance of peers declines upon entering adulthood.
While socially accepted kids often have the most opportunities and the most positive experiences, research shows that being in the popular crowd may also be a risk factor for mild to moderate deviant behaviour. Popular adolescents are the most socialized into their peer groups and thus are vulnerable to peer pressures, such as behaviours usually reserved for those of a greater maturity and understanding. Socially accepted kids are often accepted for the sheer fact that they conform well to the norms of teen culture, good and bad aspects included. Popular adolescents are more strongly associated with their peer groups' likes such as alcohol, tobacco and drugs. Some studies also show that many popular students also make lower grades than less socially accepted kids. This is possibly due to the fact that popular students may spend more time worrying about their social life rather than studying. Although there are a few risk factors correlated with popularity, deviant behaviour is often only mild to moderate. 
The Asch conformity experiments were a series of laboratory studies published in the 1950s that demonstrated a surprising degree of conformity to a majority opinion. These are also known as the Asch Paradigm. Experiments led by Solomon Asch of Swarthmore College asked groups of students to participate in a "sight test." In reality, all but one of the participants were confederates of the experimenter, and the study was really about how the remaining student would react to the confederates' behavior.
The Third Wave was an experiment to demonstrate the appeal of fascism undertaken by history teacher Ron Jones with sophomore high school students attending his Contemporary History as part of a study of Nazi Germany. The experiment took place at Cubberley High School in Palo Alto, California, during the first week of April 1967. Jones, unable to explain to his students how the German populace could claim ignorance of the extermination of the Jewish people, decided to show them instead. Jones started a movement called "The Third Wave" and convinced his students that the movement is to eliminate democracy. The fact that democracy emphasizes individuality was considered as a drawback of democracy, and Jones emphasized this main point of the movement in its motto: "Strength through discipline, strength through community, strength through action, strength through pride". The Third Wave experiment is an example of risk behavior in authoritarian peer pressure situations.
It is one useful tool in leadership. Instead of direct delegation of tasks and results demanding, employees are in this case, induced into a behaviour of self-propelled performance and innovation, by comparison feelings towards their peers. There are several ways peer pressure can be induced in a working environment. Examples include training and team meetings. In training, the team member is in contact with people with comparable roles in other organizations. In team meetings, there is an implicit comparison between every team member, especially if the meeting agenda is to present results and goal status.
Neuroimaging identifies the anterior insula and anterior cingulate as key areas in the brain determining whether people conform in their preferences in regard to its being popular with their peer group.
An explanation of how the peer pressure process works, called "the identity shift effect", is introduced by social psychologist, Wendy Treynor, who weaves together Leon Festinger's two seminal social-psychological theories (on cognitive dissonance, which addresses internal conflict, and social comparison, which addresses external conflict) into a unified whole. According to Treynor's original "identity shift effect" hypothesis, the peer pressure process works in the following way: One's state of harmony is disrupted when faced with the threat of external conflict (social rejection) for failing to conform to a group standard. Thus, one conforms to the group standard, but as soon as one does, eliminating this external conflict, internal conflict is introduced (because one has violated one's own standards). To rid oneself of this internal conflict (self-rejection), an "identity shift" is undertaken, where one adopts the group's standards as one's own, thereby eliminating internal conflict (in addition to the formerly eliminated external conflict), returning one once again to a state of harmony. Even though the peer pressure process begins and ends with one in a (conflict-less) state of harmony, as a result of conflict and the conflict resolution process, one leaves with a new identity—a new set of internalized standards.