David G Myers. Encyclopedia of Group Processes & Intergroup Relations. Editor: John M Levine & Michael A Hogg. Sage Publications. 2010.

Group polarization is the tendency for group interaction to enhance group members’ initial inclinations. This group polarization phenomenon, which occurs both in experimental settings and in everyday situations, provides a window through which researchers can observe group influence. Experiments have confirmed two group influences: informational and normative. The information gleaned from a discussion mostly favors the initially preferred alternative, thus reinforcing support for it. This entry begins with a look at how this line of research evolved, describes a variety of examples of group polarization, and discusses two possible explanations.

The Case of the “Risky Shift”

The discovery of the risky shift phenomenon illustrates how an interesting discovery often leads researchers to hasty and erroneous conclusions, which ultimately get replaced with more accurate conclusions. While trying to understand the curious finding that group discussion enhanced risk taking, investigators discovered that discussion actually tends to strengthen whatever is the initially dominant point of view, whether risky or cautious.

A research literature of more than 300 studies comparing individual and group decision making began in 1961 with a surprising finding by James Stoner, then an MIT graduate student. For his master’s thesis in industrial management, Stoner tested the commonly held belief that groups make more cautious decisions than do individuals. He invited people individually, and then in groups, to advise imagined characters how much risk to take. Here is an example of the kind of hypothetical scenario Stoner used, created for my own research:

Helen is a writer who is said to have considerable creative talent but who so far has been earning a comfortable living by writing cheap Westerns. Recently, she has come up with an idea for a potentially significant novel. If it could be written and accepted, it might have considerable literary impact and be a big boost to her career. On the other hand, if she cannot work out her idea or if the novel is a flop, she will have expended considerable time and energy without remuneration.

Imagine that you are advising Helen. Please check the lowest probability that you would consider acceptable for Helen to attempt to write the novel. Helen should attempt to write the novel if the chances that the novel will be a success are at least [intervals range from 1 in 10 to 10 in 10].

After making your decision, guess what the average person would advise.

Having marked their advice on a dozen such items, five or so individuals in Stoner’s study would then discuss and reach agreement on each item. To everyone’s amazement, given popular commentary about the conservatism of groups, the group decisions were usually riskier. During discussion, group members’ opinions converged. Curiously, however, the point toward which they converged was usually a lower (riskier) number than their initial average.

Here was an interesting puzzle. The small risky shift effect was reliable, unexpected, and without any immediately obvious explanation. Dubbed the risky shift phenomenon, this finding inspired studies of risk taking by individuals and groups. These revealed that the risky shift occurs not only when a group decides by consensus—after a brief discussion, individuals, too, will alter their decisions. What is more, researchers successfully repeated Stoner’s finding with people of varying ages and occupations in a dozen nations.

What group influences produce such an effect? And how widespread is it? Do discussions in juries, business committees, and military organizations also promote risk taking? Does this explain why teenage reckless driving, as measured by death rates, nearly doubles when a 16- or 17-year-old driver has two teenage passengers rather than none?

After several years of study, researchers discovered that the risky shift was not universal. They could write decision dilemmas on which people became more cautious after discussion. One of these featured “Roger,” a young married man with two school-age children and a secure but low-paying job. Roger can afford life’s necessities but few of its luxuries. He hears that the stock of a relatively unknown company may soon triple in value if its new product is favorably received—or decline considerably if it does not sell. Roger has no savings. To invest in the company, he is considering selling his life insurance policy.

Is there a general principle that predicts both the tendency to give riskier advice after discussing Helen’s situation and more cautious advice after discussing Roger’s? Most people advise Helen to take a greater risk than Roger, even before talking with others. Group discussion then accentuates these initial leanings. Thus, group members discussing Roger’s dilemma become, on average, more risk averse than they were before discussion.

Do Groups Intensify Opinions?

Realizing that this group phenomenon was not a consistent shift toward increased risk, researchers reconceived it as a phenomenon in which discussion typically strengthens the average inclination of group members. This idea led investigators to propose what French researchers Serge Moscovici and Marisa Zavalloni in 1969 called group polarization, the tendency for group discussion to enhance group members’ initial leanings.

Group Polarization Experiments

This new view of the changes induced by group discussion prompted experimenters to have people discuss attitude statements that most of them favored or most of them opposed. Will group interaction not only lead risk takers to become riskier, but bigots to become despisers, and givers to become more philanthropic? The following are examples chosen from dozens of studies that confirm such group polarization:

• Moscovici and Zavalloni observed that discussion enhanced French students’ initially positive attitude toward their president and negative attitude toward Americans.
• Mititoshi Isozaki found that Japanese university students gave more pronounced judgments of “guilty” after discussing a traffic case.
• Markus Brauer and his coworkers found that French students’ dislike for certain other people was exacerbated after discussing their shared negative impressions.
• Glen Whyte reported that groups accentuate the “too much invested to quit” phenomenon that has cost many businesses huge sums of money. Canadian business students imagined themselves having to decide whether to invest more money in the hope of preventing losses in various failing projects (for example, whether to make a high-risk loan to protect an earlier investment). They exhibited the typical effect: 72% reinvested money they would probably not have invested if they were considering it as a new investment on its own merits. When making the same decision in groups, 94% opted for reinvestment.

Another research strategy has been to pick issues on which opinions are divided and then isolate people who hold the same view. Does discussion with like-minded people strengthen shared views, and does it magnify the attitude gap that separates the two sides? George Bishop and David Myers investigated this question by setting up groups of relatively prejudiced and unprejudiced high school students and asking them to respond—before and after discussion—to issues involving racial attitudes, such as property rights versus open housing. They found that the discussions among like-minded students did indeed increase the initial gap between the two groups.

Group Polarization in Everyday Life

In everyday life, people associate mostly with others whose attitudes are similar to their own. Does everyday group interaction with like-minded friends intensify shared attitudes? Do nerds become nerdier and jocks jockier?

It happens. The self-segregation of boys into all-male groups and of girls into all-female groups accentuates over time their initially modest gender differences, notes Eleanor Maccoby. Boys with boys become gradually more competitive and action oriented in their play, while girls with girls become more relationally oriented.

On U.S. federal appellate court cases, “Republican-appointed judges tend to vote like Republicans and Democratic-appointed judges tend to vote like Democrats,” David Schkade and Cass Sunstein observed in 2003. That’s understandable. But, as these researchers noted, such tendencies are accentuated when judges are among other like-minded judges: “A Republican appointee sitting with two other Republicans votes far more conservatively than when the same judge sits with at least one Democratic appointee. A Democratic appointee, meanwhile, shows the same tendency in the opposite ideological direction.”

Group Polarization in Schools

Another real life parallel to the laboratory phenomenon is what education researchers have called the accentuation phenomenon: Over time, initial differences among groups of college students become accentuated. If the first-year students at College X are initially more intellectual than the first-year students at College Y, that gap is likely to increase by the time they graduate. Likewise, compared with fraternity and sorority members, independents tend to have more liberal political attitudes, a difference that grows with time in college. Researchers believe this results partly from group members reinforcing shared inclinations.

Group Polarization in Communities

Polarization also occurs in communities, as people self-segregate. Liberal communities attract liberals and become more liberal, while conservative places attract conservatives and become more conservative. Neighborhoods become echo chambers, with opinions ricocheting off kindred-spirited friends. In the United States, the end result has become a more divided country. The percentage of landslide counties—those voting 60% or more for one presidential candidate—nearly doubled between 1976 and 2000. The percentage of entering collegians (in UCLA’s annual survey) declaring themselves politically “middle of the road” dropped from 60% in 1983 to 43% in 2008, with corresponding increases in those declaring themselves on the right or the left.

On college campuses, the clustering of students into mostly White sororities and fraternities and into ethnic minority student organizations tends to strengthen social identities and to increase antagonisms among the social groups.

In laboratory studies, the competitive relationships and mistrust that individuals often display when playing games with one another often worsen when the players are in groups. During actual community conflicts, like-minded people associate increasingly with one another, amplifying their shared beliefs. Gang delinquency emerges from a process of mutual reinforcement within neighborhood gangs, whose members share attributes and hostilities. If “a second out-of-control 15-year-old moves in [on your block],” surmised David Lykken in 1997, “the mischief they get into as a team is likely to be more than merely double what the first would do on his own…. A gang is more dangerous than the sum of its individual parts.” Indeed, “unsupervised peer groups” are the strongest predictor of a neighborhood’s crime victimization rate, reported Bonita Veysey and Steven Messner. Moreover, experimental interventions that take delinquent adolescents and group them with other delinquents actually—no surprise to anygroup polarization researcher—increase the rate of problem behavior.

Group Polarization on the Internet

E-mail and electronic chat rooms offer a potential new medium for group interaction. By the beginning of the new century, 85% of Canadian teens were using the Internet for an average of 9.3 hours weekly. Its countless virtual groups enable peacemakers and neo-Nazis, geeks and Goths, conspiracy theorists and cancer survivors to isolate themselves with like-minded others and find support for their shared concerns, interests, and suspicions. Without the nonverbal nuances of face-to-face contact, will such discussions produce group polarization? Will peacemakers become more pacifistic and militia members more terror prone? E-mail, Google, and chat rooms “make it much easier for small groups to rally like-minded people, crystallize diffuse hatreds and mobilize lethal force,” observed Robert Wright in 2003. As broadband spreads, Internet-spawned polarization will increase, he speculated.

Group Polarization in Terrorist Organizations

From their analysis of terrorist organizations around the world, Clark McCauley and Mary Segal surmised that terrorism does not erupt suddenly. Rather, it arises among people whose shared grievances bring them together. As they interact in isolation from moderating influences, they become progressively more extreme. The social amplifier brings the signal in more strongly. The result is violent acts that the individuals, apart from the group, would never have committed.

For example, the September 11, 2001, terrorists were bred by a long process that engaged the polarizing effect of interaction among the like-minded. The process of becoming a terrorist, noted a National Research Council panel, isolates individuals from other belief systems, dehumanizes potential targets, and tolerates no dissent. Over time, group members come to categorize the world as “us” and “them.” Ariel Merari, an investigator of Middle Eastern and Sri Lankan suicide terrorism, believes the key to creating a terrorist suicide is the group process. In 2002, he wrote: “To the best of my knowledge, there has not been a single case of suicide terrorism which was done on a personal whim.” According to one analysis of terrorists who were members of the Salafi Jihad—an Islamic fundamentalist movement, of which al Qaeda is a part—70% joined while living as expatriates. After moving to foreign places in search of jobs or education, they became mindful of their Muslim identity and often gravitated to mosques and moved in with other expatriate Muslims, who sometimes recruited them into cell groups that provided “mutual emotional and social support” and “development of a common identity.” Massacres, similarly, have been found to be group phenomena. The violence is enabled and escalated by the killers egging each other on.

Explaining Polarization

Why do groups adopt stances that are more exaggerated than that of their average individual member? Researchers hoped that solving the mystery of group polarization might provide some insights into group influence. Solving small puzzles sometimes provides clues for solving larger ones. Among several proposed theories of group polarization, two have survived scientific scrutiny. One deals with the arguments presented during a discussion, the other with how members of a group view themselves vis-à-vis the other members. The first idea is an example of informational influence (influence that results from accepting evidence about reality). The second is an example of normative influence (influence based on a person’s desire to be accepted or admired by others).

Informational Influence

According to the best-supported explanation, group discussion elicits a pooling of ideas, most of which favor the dominant viewpoint. Ideas that are common knowledge to group members will often be brought up in discussion or, even if unmentioned, will influence their discussion. Other ideas may include persuasive arguments that some group members had not previously considered. When discussing Helen the writer, someone may say, “Helen should go for it, because she has little to lose. If her novel flops, she can always go back to writing cheap Westerns.” Such statements often entangle information about the person’s arguments with cues concerning the person’s position on the issue. But when people hear relevant arguments without learning the specific stands other people assume, they still shift their positions. Arguments, in and of themselves, matter.

But there is more to attitude change than merely hearing someone else’s arguments. Active participation in discussion produces more attitude change than does passive listening. Participants and observers hear the same ideas, but when participants express them in their own words, the verbal commitment magnifies the impact. The more group members repeat one another’s ideas, the more they rehearse and validate them. Just privately writing out one’s ideas in preparation for an electronic discussion tends to polarize attitudes somewhat.

Normative Influence

A second explanation of polarization involves comparison with others. As Leon Festinger argued in his influential theory of social comparison, we humans want to evaluate our opinions and abilities, something we can do by comparing our views with those of others. We are most persuaded by people in our reference groups—groups with which we identify. Moreover, wanting people to like us, we may express stronger opinions after discovering that others share our views.

When we ask people to predict how others would respond to items such as Helen’s dilemma, they typically exhibit pluralistic ignorance: They don’t realize how strongly others support the socially preferred tendency (in this case, writing the novel). A typical person will advise writing the novel even if its chance of success is only 4 in 10 but will estimate that most other people would require 5 or 6 in 10. (This finding is reminiscent of the self-serving bias: People tend to view themselves as better-than-average embodiments of socially desirable traits and attitudes.) When the discussion begins, most people discover they are not outshining the others as they had supposed. In fact, some others are ahead of them, having taken an even stronger position in favor of writing the novel. No longer restrained by a misperceived group norm, they are liberated to voice their preferences more strongly.

This social comparison theory prompted experiments that exposed people to others’ positions but not to their arguments. This is roughly the experience we have when reading the results of an opinion poll or of exit polling on election day. When people learn others’ positions—without prior commitment and without discussion or sharing of arguments—will they adjust their responses to maintain a socially favorable position? Indeed, they will. This comparison-based polarization is usually less than that produced by a lively discussion. Still, it is surprising that, instead of simply conforming to the group average, people often go it one better.

Group polarization research illustrates the complexity of social psychological inquiry. As much as we like our explanations of a phenomenon to be simple, one explanation seldom accounts for all the data. Because people are complex, more than one factor frequently influences an outcome. In group discussions, persuasive arguments predominate on issues that have a factual element (“Is he guilty of the crime?”). Social comparison sways responses on value-laden judgments (“How long a sentence should he serve?”). On the many issues that have both factual and value-laden aspects, the two factors work together. Discovering that others share one’s feelings (social comparison) unleashes arguments (informational influence) supporting what everyone secretly favors.