Group psychology focuses on organizations in which individuals relinquish some of their control within a group setting. Cognitive gestalt psychologists, such as Kurt Lewin (1890-1947), were instrumental in developing group psychology in the 1930s.
In his seminal work on group psychology, Group Psychology and the Analysis of the Ego,Sigmund Freud (1856-1939), defined a group as "a number of individuals who have put one and the same object in the place of their ego ideal and have consequently identified themselves with one another in their ego." The most basic definition is two or more individuals connected by social relationships. Group members typically share a common identity, interact, and influence each other. They have a number of emergent qualities including roles, such as a group leader, and norms, rules and expectations. An aggregate, such people walking along a particular stretch of sidewalk at a particular time, does not constitute a group. However, Henri Tajfel (1919-1982), in his book Human Groups and Social Categories, wrote about strangers who were organized into two groups. Each group favored members of their own group over the others even without knowing or seeing who else was in their group. Groups often define and limit themselves by an initiation procedure, or membership fee.
Deindividuation, a reduced state of self-awareness with a feeling of anonymity in a group, is common. This can reduce inhibition and self-restraint. This can result in anti-social behavior such as crowd violence, mob rioting and abuse of unregulated multi-user online chat sites. This is also an explanation for decreased productivity in a group, such as that identified by Max Ringelmann (1861-1931). In a phenomenon sometimes called "social loafing," Ringelmann observed that individuals pulled harder on a rope working alone than working together.
Freud suggested that groups are held together by the libido, or life drive, overcoming the narcissism and hatred that could distance members from one another. He suggested that a group could come apart through the loss of libidinal bonds to the leader or among members.
Groups tend to promote consensus, sometimes at the expense of minority or individual opinions. Solomon Asch (1907-1996) conducted an experiment that showed the power of consensus. Participants in the experiment were asked to judge the length of a line. Each subject was placed in a group, the rest of whose members had been told to lie about the line length. Of the subjects, 75 percent answered incorrectly at least once, in order to conform to the rest of the group. It was found that 5 percent answered the same as the rest every time, in order to conform with the group even though the answer was against their own judgment.
Group polarization occurs when members' views become more extreme after group discussion. Polarization may be the result of "groupthink," a collective thinking defect that is characterized by a premature consensus or an incorrect assumption of consensus. This is likely to occur where the group is isolated, or due to a dominant leader. Kurt Lewin characterized organizational management styles as authoritarian, democratic and laissez-faire. Irving Janis (1918-1990) argued, in Victims of Groupthink, that the decisions by Presidents Kennedy, Johnson and Nixon to extend the war in Vietnam were due to groupthink, which rendered them unable to explore alternatives. Another challenge identified in groups is the failure of groups to share information.
In the Stanford Prison Experiment, Philip Zimbardo (1933-) organized 24 Stanford college students to be "prisoners" or "guards" in a mock prison located in the basement of the psychology building at Stanford. The study ended eight days early due to trauma and depression experienced by the "prisoners" and "sadism" on the part of the guards.
Stanley Milgram (1933-1984) was an American social psychologist most noted for his controversial study known as the Milgram Experiment. The volunteer subject was given the role of teacher, and the confederate (an actor), the role of learner. The teacher read a question and if the answer was incorrect, the teacher was led to believe that he was administering a shock to the learner, with the voltage increasing in 15-volt increments for each wrong answer. In reality, there were no shocks. A tape recorder played pre-recorded sounds for each shock level. Some test subjects paused at 135 volts and began to question the purpose of the experiment. Most subjects continued after being assured that they would not be held responsible. Of the participants, 24 out of 40 administered the maximum 450-volt shock, though many were very uncomfortable doing so. The experiment was repeated with women, and the results were the same. Milgram explained the behavior as conformism as described by Asch, whereby individuals prefer to leave decision making to the group and its hierarchy. Milgram suggested that once the person saw themselves as the instrument for carrying out another person's wishes, obedience followed because they no longer felt responsible for their actions.