A group can influence our behavior even when we are not part of a group. The theory of social facilitation developed by Robert Zajonc implies that the mere presence of others is a source of general arousal that will result in superior performance on simple or well-learned tasks and inferior performance on poorly learned or complex tasks. Groups have been analyzed in a variety of ways. Research on group size reveals the apparent existence of social loafing . The effort exerted by an individual to perform a task is less when working with others than when working alone and the greater the size of the group involved, the greater the reduction of effort.
Group think is another related phenomenon.
It refers to the tendency of group members to seek concurrence with each other, and frequently results in a process by which groups may come to make poor decisions. Generally, group interaction tends to lead to the polarization of responses. The opinions resulting from group discussion are more extreme and are more tolerant of a level of risk than the opinions of individuals prior to group discussion. Non-laboratory examples of groups in action include juries, families, and encounter groups. Although each of these groups exhibit some unique properties, each also demonstrates the applicability of general social-psychological principles.