In social psychology, pluralistic ignorance is a situation in which a majority of group members privately reject a norm, but go along with it because they assume, incorrectly, that most others accept it. This is also described as "no one believes, but everyone thinks that everyone believes". Pluralistic ignorance is a bias about a social group, held by the members of that social group.
Prentice and Miller found that, on average, private levels of comfort with drinking practices on campus were much lower than the perceived average. In the case of men, they found a shifting of private attitudes toward this perceived norm, a form of cognitive dissonance. Women, on the other hand, were found to have an increased sense of alienation on the campus but lacked the attitude change detected in men, presumably because norms related to alcohol consumption on campus are much more central for men than for women. Research has shown that pluralistic ignorance plagues not only those who indulge, but also those who abstain: from gambling, smoking and drinking and among some who follow vegetarianism. The latter has found that pluralistic ignorance can be caused by the structure of the underlying social network, not cognitive dissonance.
The theory of pluralistic ignorance was studied by Floyd Henry Allport and his students Daniel Katz and Richard Schanck. He produced studies of racial stereotyping and prejudice, and attitude change, and his pursuit of the connections between individual psychology and social systems helped to found the field of organizational psychology. Elisabeth Noelle-Neumann, in her spiral of silence theory, argued that media biases lead to pluralistic ignorance.
Pluralistic ignorance was blamed for exacerbating support for racial segregation in the United States. It has also been named a reason for the illusory popular support that kept the Communist Party of the Soviet Union in power, as many opposed the regime but assumed that others were supporters of it. Thus, most people were afraid to voice their opposition.
Another case of pluralistic ignorance concerns drinking on campus in countries where alcohol use is prevalent at colleges and universities. Students drink at weekend parties and sometimes at evening study breaks. Many drink to excess, some on a routine basis. The high visibility of heavy drinking on campus, combined with reluctance by students to show any public signs of concern or disapproval, gives rise to pluralistic ignorance: Students believe that their peers are much more comfortable with this behavior than they themselves feel.
Hans Christian Andersen's fairy tale "The Emperor's New Clothes" is a famous fictional case of pluralistic ignorance. In this story two con artists come into the Emperor's kingdom and convince him that they make the finest clothes in all of the land that can only be seen by anyone who was not stupid. The con artists continued to steal gold, silk and other precious items for their "unique creation". Out of fear for being seen as stupid, all of the emperor's men and townspeople kept silent about the fact they could not see the emperor's clothes until finally a small child comes forth and says that the emperor isn't wearing any clothes. Once the child is willing to admit that he cannot see any clothes on the emperor, the emperor and townspeople finally admit that the emperor has been tricked and that there was never an outfit being made.
Pluralistic ignorance has also been blamed for large majorities of the public remaining silent on climate change—while 'solid majorities' of the American and UK public are concerned about climate change, most erroneously believe they are in the minority with their concern. It has been suggested that pollution-intensive industries have contributed to the public's underestimation of public support for climate solutions. For example, in the U.S., support for pollution pricing is high, yet public perception of public support is much lower.
Men's conceptions of how they are expected to conform to norms of masculinity present additional examples of pluralistic ignorance. Specifically, most college age men are uncomfortable with other men "bragging about sexual acts and giving details," but erroneously believe themselves to be in the minority for their discomfort. Similarly, college age men underestimate other men's "desire to make sure they have consent when sexually active". This "role-conflict" can have deleterious consequences for men's physical and mental health, as well as for society.
Netflix's "Derren Brown: The Push" explores some aspects of these concepts. 
According to a 2020 study, the vast majority of young married men in Saudi Arabia express private beliefs in support of women working outside the home but they substantially underestimate the degree to which other similar men support it. Once they become informed about the widespread nature of the support, they increasingly help their wives obtain jobs.
Pluralistic ignorance has been linked to a wide range of deleterious consequences. Victims of pluralistic ignorance see themselves as deviant members of their peer group: less knowledgeable than their classmates, more uptight than their peers, less committed than their fellow board members, less competent than their fellow nurses (see the Dunning–Kruger effect operating in the opposite direction). This can leave them feeling bad about themselves and alienated from the group or institution of which they are a part. In addition, pluralistic ignorance can lead groups to persist in policies and practices that have lost widespread support: This can lead college students to persist in heavy drinking, corporations to persist in failing strategies, and governments to persist in unpopular foreign policies. At the same time, it can prevent groups from taking actions that would be beneficial in the long run: actions to intervene in an emergency, for example, or to initiate a personal relationship.
Pluralistic ignorance can be dispelled, and its negative consequences alleviated, through education. For example, students who learn that support for heavy drinking practices is not as widespread as they thought drink less themselves and feel more comfortable with the decision not to drink. Alcohol intervention programs now routinely employ this strategy to combat problem drinking on campus.
Pluralistic ignorance can be contrasted with the false consensus effect. In pluralistic ignorance, people privately disdain but publicly support a norm (or a belief), while the false consensus effect causes people to wrongly assume that most people think like they do, while in reality most people do not think like they do (and express the disagreement openly). For instance, pluralistic ignorance may lead a student to drink alcohol excessively because she believes that everyone else does that, while in reality everyone else also wishes they could avoid binge drinking, but no one expresses that due to the fear of being ostracized. A false consensus for the same situation would mean that the student believes that most other people do not enjoy excessive drinking, while in fact most other people do enjoy that and openly express their opinion about it.
A study undertaken by Greene, House, and Ross used simple circumstantial questionnaires on Stanford undergrads to gather information on the false consensus effect. They compiled thoughts on the choice they felt people would or should make, considering traits such as shyness, cooperativeness, trust, and adventurousness. Studies found that when explaining their decisions, participants gauged choices based on what they explained as "people in general" and their idea of "typical" answers. For each of the stories those subjects said that they personally would follow a given behavioral alternative also tended to rate that alternative as relatively probable for "people in general": those subjects who claimed that they would reject the alternative tended to rate it as relatively improbable for "people in general". It was evident that the influence of the subjects' own behavior choice affected the estimates of commonness. Although it would seem as if the two are built on the same premise of social norms, they take two very oppositional stances on a similar phenomenon. The false consensus effect considers that in predicting an outcome, people will assume that the masses agree with their opinion and think the same way they do on an issue, whereas the opposite is true of pluralistic ignorance, where the individual does not agree with a certain action but go along with it anyway, believing that their view is not shared with the masses (which is usually untrue).
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