Group polarization effects have been demonstrated to exaggerate the inclinations of group members after a discussion. A military term for group polarization is "incestuous amplification".


Study of this effect has shown that after participating in a discussion group, members tend to advocate more extreme positions and call for riskier courses of action than individuals who did not participate in any such discussion. This phenomenon was originally coined risky shift but was found to apply to more than risk, so the replacement term choice shift has been suggested.

In addition, attitudes such as racial and sexual prejudice tend to be reduced (for already low-prejudice individuals) and inflated (for already high-prejudice individuals) after group discussion.

Group polarization has been used to explain the decision-making of a jury, particularly when considering punitive damages in a civil trial. Studies have shown that after deliberating together, mock jury members often decided on punitive damage awards that were larger or smaller than the amount any individual juror had favored prior to deliberation. The studies indicated that when the jurors favored a relatively low award, discussion would lead to an even more lenient result, while if the jury was inclined to impose a stiff penalty, discussion would make it even harsher.

Developments in the study of group polarization:

The study of group polarization began with an unpublished 1961 Master's thesis by MIT student James Stoner, who observed the so-called "risky shift", meaning that a group’s decisions are riskier than the average of the individual decisions of members before the group met. The discovery of the risky shift was considered surprising and counterintuitive, especially since earlier work in the 1920s and 1930s by Allport and other researchers suggested that individuals made more extreme decisions than did groups, leading to the expectation that groups would make decisions that would conform to the average risk level of its members. The seemingly counterintuitive findings of Stoner led to a flurry of research around the risky shift, which was originally thought to be a special case exception to the standard decision-making practice. By the late 1960s, however, it had become clear that the risky shift was just one type of many attititudes that became more extreme in groups, leading Moscovici and Zavalloni to term the overall phenomenon "group polarization".

Thus began a decade-long period of examination of the applicability of group polarization to a number of fields, ranging from political attititudes to religion, in both lab and field settings. Basic studies of group polarization tapered off, but research on the topic continued. Group polarization was well-established, but remained non-obvious and puzzling because its mechanisms were not understood.

Mechanisms of polarization:

Almost as soon as the phenomenon of group polarization was discovered, a variety of hypotheses were suggested for the mechanisms for its action. These explanations were gradually winnowed down and grouped together until two primary mechanisms remained, social comparison and influence. Social comparison approaches, sometimes called interpersonal comparison, were based on social psychological views of self-perception and the drive of individuals to appear socially desirable . The second major mechanism is informational influence, which is also sometimes referred to as persuasive argument theory, or PAT. PAT holds that individual choices are determined by individuals weighing remembered pro and con arguments. These arguments are then applied to possible choices, and the most positive is selected. As a mechanism for polarization, group discussion shifts the weight of evidence as each individual exposes their pro and con arguments, giving each other new arguments and increasing the stock of pro arguments in favor of the group tendency, and con arguments against the group tendency. The persuasiveness of an argument depends on two factors – originality and its validity. According to PAT, a valid argument would hold more persuasive weight than a non-valid one. Originality has come to be understood in terms of the novelty of an argument. A more novel argument would increase the likelihood that it is an addition to the other group members’ pool of pro and con arguments, rather than a simple repetition.

In the 1970s, significant arguments occurred over whether persuasive argumentation alone accounted for group polarization. Daniel Isenberg’s 1986 meta-analysis of the data gathered by both the persuasive argument and social comparison camps succeeded, in large part, in answering the questions about predominant mechanisms. Isenberg concluded that there was substantial evidence that both effects were operating simultaneously, and that PAT operated when social comparison did not, and vice-versa. Isenberg did discover that PAT did seem to have a significantly stronger effect, however.