In social psychology, group polarization refers to the tendency for a group to make decisions that are more extreme than the initial inclination of its members. These more extreme decisions are towards greater risk if individuals' initial tendencies are to be risky and towards greater caution if individuals' initial tendencies are to be cautious. The phenomenon also holds that a group's attitude toward a situation may change in the sense that the individuals' initial attitudes have strengthened and intensified after group discussion, a phenomenon known as attitude polarization.

Overview Group polarization is an important phenomenon in social psychology and is observable in many social contexts. For example, a group of women who hold moderately feminist views tend to demonstrate heightened pro-feminist beliefs following group discussion. Similarly, studies have shown that after deliberating together, mock jury members often decided on punitive damage awards that were either 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. Moreover, in recent years, the Internet and online social media have also presented opportunities to observe group polarization and compile new research. Psychologists have found that social media outlets such as Facebook and Twitter demonstrate that group polarization can occur even when a group is not physically together. As long as the group of individuals begins with the same fundamental opinion on the topic and a consistent dialogue is kept going, group polarization can occur.

Research has suggested that well-established groups suffer less from polarization, as do groups discussing problems that are well known to them. However, in situations where groups are somewhat newly formed and tasks are new, group polarization can demonstrate a more profound influence on decision-making.

Attitude polarization

Attitude polarization, also known as belief polarization and the polarization effect, is a phenomenon in which a disagreement becomes more extreme as the different parties consider evidence on the issue. It is one of the effects of confirmation bias: the tendency of people to search for and interpret evidence selectively, to reinforce their current beliefs or attitudes. When people encounter ambiguous evidence, this bias can potentially result in each of them interpreting it as in support of their existing attitudes, widening rather than narrowing the disagreement between them.

The effect is observed with issues that activate emotions, such as political "hot-button" issues. For most issues, new evidence does not produce a polarization effect. For those issues where polarization is found, mere thinking about the issue, without contemplating new evidence, produces the effect. Social comparison processes have also been invoked as an explanation for the effect, which is increased by settings in which people repeat and validate each other's statements. This apparent tendency is of interest not only to psychologists, but also to sociologists and philosophers.

Empirical findings Since the late 1960s, psychologists have carried out a number of studies on various aspects of attitude polarization.

In 1979, Charles Lord, Lee Ross and Mark Lepper performed a study in which they selected two groups of people, one group strongly in favor of capital punishment, the other strongly opposed. The researchers initially measured the strength with which people held their position. Later, both the pro- and anti-capital punishment people were put into small groups and shown one of two cards, each containing a statement about the results of a research project written on it. For example:Kroner and Phillips (1977) compared murder rates for the year before and the year after adoption of capital punishment in 14 states. In 11 of the 14 states, murder rates were lower after adoption of the death penalty. This research supports the deterrent effect of the death penalty.or:Palmer and Crandall (1977) compared murder rates in 10 pairs of neighboring states with different capital punishment laws. In 8 of the 10 pairs, murder rates were higher in the state with capital punishment. This research opposes the deterrent effect of the death penalty.The researchers again asked people about the strength of their beliefs about the deterrence effect of the death penalty, and, this time, also asked them about the effect that the research had had on their attitudes.

In the next stage of the research, the participants were given more information about the study described on the card they received, including details of the research, critiques of the research, and the researchers' responses to those critiques. The participants' degree of commitment to their original positions were re-measured, and the participants were asked about the quality of the research and the effect the research had on their beliefs. Finally, the trial was rerun on all participants using a card that supported the opposite position to that they had initially seen.

The researchers found that people tended to believe that research that supported their original views had been better conducted and was more convincing than research that didn't. Whichever position they held initially, people tended to hold that position more strongly after reading research that supported it. Lord et al. point out that it is reasonable for people to be less critical of research that supports their current position, but it seems less rational for people to significantly increase the strength of their attitudes when they read supporting evidence. When people had read both the research that supported their views and the research that did not, they tended to hold their original attitudes more strongly than before they received that information. These results should be understood in the context of several problems in the implementation of the study, including the fact the researchers changed the scaling of the outcome of the variable, so measuring attitude change was impossible, and measured polarization using a subjective assessment of attitude change and not a direct measure of how much change had occurred.

Choice shifts Group polarization and choice shifts are similar in many ways; however, they differ in one distinct way. Group polarization refers to attitude change on the individual level due to the influence of the group, and choice shift refers to the outcome of that attitude change; namely, the difference between the average group members' pre-group discussion attitudes and the outcome of the group decision.

Risky and cautious shifts are both a part of a more generalized idea known as group-induced attitude polarization. Though group polarization deals mainly with risk-involving decisions and/or opinions, discussion-induced shifts have been shown to occur on several non-risk-involving levels. This suggests that a general phenomenon of choice-shifts exists apart from only risk-related decisions. Stoner (1968) found that a decision is impacted by the values behind that circumstances of the decision. The study found that situations that normally favor the more risky alternative increased risky shifts. More so, situations that normally favor the cautious alternative increased cautious shifts. These findings also show the importance of previous group shifts. Choice shifts are mainly explained by largely differing human values and how highly these values are held by an individual. According to Moscovici et al. (1972) interaction within a group and differences of opinion are necessary for group polarization to take place. While an extremist in the group may sway opinion, the shift can only occur with sufficient and proper interaction within the group. In other words, the extremist will have no impact without interaction. Also, Moscovici et al. found individual preferences to be irrelevant; it is differences of opinion which will cause the shift. This finding demonstrates how one opinion in the group will not sway the group; it is the combination of all the individual opinions that will make an impact.

History and origins The study of group polarization can be traced back to an unpublished 1961 Master's thesis by MIT student James Stoner, who observed the so-called "risky shift". The concept of risky shift maintains that a group's decisions are riskier than the average of the individual decisions of members before the group met.

In early studies, the risky-shift phenomenon was measured using a scale known as the Choice-Dilemmas Questionnaire. This measure required participants to consider a hypothetical scenario in which an individual is faced with a dilemma and must make a choice to resolve the issue at hand. Participants were then asked to estimate the probability that a certain choice would be of benefit or risk to the individual being discussed. Consider the following example:"Mr. A, an electrical engineer, who is married and has one child, has been working for a large electronics corporation since graduating from college five years ago. He is assured of a lifetime job with a modest, though adequate, salary and liberal pension benefits upon retirement. On the other hand, it is very unlikely that his salary will increase much before he retires. While attending a convention, Mr. A is offered a job with a small, newly founded company which has a highly uncertain future. The new job would pay more to start and would offer the possibility of a share in the owner- ship if the company survived the competition of the larger firms."Participants were then asked to imagine that they were advising Mr. A. They would then be provided with a series of probabilities that indicate whether the new company that offered him a position is financially stable. It would read as following

"Please check the lowest probability that you would consider acceptable to make it worthwhile for Mr. A to take the new job."

____The chances are 1 in 10 that the company will prove financially sound.

____The chances are 3 in 10 that the company will prove financially sound.

____The chances are 5 in 10 that the company will prove financially sound.

____The chances are 7 in 10 that the company will prove financially sound.

____The chances are 9 in 10 that the company will prove financially sound.

____Place a check here if you think Mr. A should not take the new job no matter what the probabilities.

Individuals completed the questionnaire and made their decisions independently of others. Later, they would be asked to join a group to reassess their choices. Indicated by shifts in the mean value, initial studies using this method revealed that group decisions tended to be relatively riskier than those that were made by individuals. This tendency also occurred when individual judgments were collected after the group discussion and even when the individual post-discussion measures were delayed two to six weeks.Forsyth, D.R. (2010) Group Dynamics