Peer pressure (or social pressure) is the direct influence on people by peers, or the effect on an individual who gets encouraged to follow their peers by changing their attitudes, values or behaviors to conform to those of the influencing group or individual. This can result in either a positive or negative effect, or both. Social groups affected include both membership groups, in which individuals are "formally" members (such as political parties and trade unions), and cliques, in which membership is not clearly defined. However, a person does not need to be a member or be seeking membership of a group to be affected by peer pressure. Peer pressure can decrease one's confidence.