“Having at least one person with different political or religious views in an individual's close personal network is associated with significantly less extreme beliefs in that individual.”

Individuals who reported very few and very many strong social connections were more likely than others to support political violence or be personally willing to engage in it. Those with 1–4 strong connections with people who mostly share beliefs about political violence were more likely to endorse non-political violence, while zero connections positively associated with endorsement of political violence in general. Findings suggest increasing prosocial connections could prevent violence, aligning with intergroup contact theory that bridging differences reduces polarization.

With 713 independent samples from 515 studies, the meta-analysis finds that intergroup contact typically reduces intergroup prejudice. A global indicator of Allport’s optimal contact conditions demonstrates that contact under these conditions typically leads to even greater reduction in prejudice.

Research focused on the role of social networks in radicalizing individuals to terrorism or violent extremism, including previous NIJ-sponsored research, has shown patterns of echo chambers reinforcing extreme views. Cross-cutting ties are not directly examined, but homogeneous networks contribute to radicalization pathways.

We find that partisan echo chambers increase both policy and affective polarization compared to mixed discussion groups. Our findings, therefore, suggest that increasing cross-partisan discussion, even when debating controversial issues, can ameliorate affective polarization.

Deliberative theory suggests that politically dissimilar social ties should decrease extremism and attenuate the influence exerted by radical and ideologically homogeneous online groups. This is because encountering dissimilar opinions would encourage people to take others’ views into account in reconsidering their predilections, foster understanding. However, empirical results showed that politically dissimilar strong ties did not decrease extremism; instead, both similar and dissimilar offline environments appeared to increase extremism among neo-Nazis.

As political psychologist Lilliana Mason has shown, greater homogeneity within groups with fewer cross-cutting ties allows people to form clearer in- and out-groups, priming them for conflict. When many identities align, belittling any one of them can trigger humiliation and anger. Such feelings are heightened by policy differences but are not about policy; they are personal, and thus are more powerful.

Our model of collective decision making is analytically tractable and shows how diverse populations can make better decisions than homogeneous ones, extending previous results. ... in heterogeneous networks a wrong first choice is usually made by hasty, uninformed agents and only convinces others who are similarly quick to decide. Cautious agents can observe the decisions of early adopters and make the right choice. Thus, in diverse groups decisions by unreliable agents, even when wrong, can reveal the better option.

The Contact Hypothesis is a psychological theory that suggests that direct contact between members of different social or cultural groups can reduce prejudice, improve intergroup relations, and promote mutual understanding. The researchers found that, in general, greater levels of intergroup contact were associated with lower levels of prejudice.

The moderation effect has been replicated in numerous studies, and there is consistent evidence from a variety of research settings that both the amount and quality of contact with individual outgroup members have stronger, more beneficial and more generalised effects on intergroup attitudes when the contact person is seen as ‘typical’ of the outgroup.

Contact, then, has a real and tangible effect on reducing prejudice – both at the explicit and implicit level. Indeed, the role of contact in reducing prejudice is now so well documented that it justifies being referred to as intergroup contact theory.

The partisan diversity of people's friend networks is linked to how people feel about the members of the other party, particularly among Republicans. Those who have at least some close friends in the other party tend to feel less coldly toward people in that party than those with few friends of the opposing party.

Chris Bail, founder of Duke University's Polarization Lab, states that contrary to popular belief, the problem is not solely echo chambers. His research found that when Republicans and Democrats were exposed to messages from the opposing side via bots on Twitter, both groups expressed *more* extreme views rather than moderating them, suggesting that exposure to contradictory information can sometimes strengthen existing viewpoints.

Participants reporting higher levels of intergroup contact gave higher ratings of wrongfulness of exclusion and lower frequency estimations of race-based exclusion.

In times of personal crisis, individuals may turn to radical ideologies that promise clarity and a sense of belonging, often framed through religious or ideological lenses. Those most susceptible to online radicalization are experiencing identity crises prior to their social media exposure to hate.

“What we found is that friendship tends to reduce the range of political opinions, particularly among friends with complementary views,” says Professor Zenou. “For example, friends tended to join the same political association together and then that tended to reinforce their views. However, if the students had completely opposing views, friendship didn't change those views.”

The Networks of Belief theory allows researchers to model the interplay of individuals and the people around them, of perceived and actual beliefs, and of various levels of attention. The second premise is that people want to reduce the dissonance in their beliefs, personally, socially, and externally.

It finds people who have experienced significant adversity in their lives are more likely to gravitate toward an extreme spot on the ideological spectrum. The researchers found that, “regardless of direction, everyone is moved by adversity to become more polarized in their beliefs.”

But when group boundaries are eliminated entirely, people have almost nothing in common with their neighbors and therefore very little influence over one another, making it impossible to spread complex ideas. What this study shows is that preserving group boundaries is actually necessary for complex ideas to become accepted across diverse populations.

This work demonstrates how expectation-based updating with respect to unknown source reliabilities and the fact that sources are part of wider social networks can lead to agents over-estimating evidence and developing more extreme, overconfident beliefs than objectively justified. This process can establish a confirmation bias among agents.

The complexity of overlapping social networks allows unintended consequences to emerge. Connections between different networks can enable beliefs and behaviours to emerge and cascade until they become widespread. For example, after being exposed to extremist views on social media, an individual might spread them within a family or neighbourhood.

The "Echo Chamber Effect" refers to a phenomenon in which an individual's beliefs and views are reinforced by exposure to information that aligns with their preexisting opinions. This effect often occurs within isolated communities, or "tribes," that share common beliefs, leading to polarized perspectives and a reduced understanding of opposing viewpoints.

Classic intergroup contact theory posits that interpersonal contact between members of different groups, under optimal conditions, reduces prejudice and intergroup hostility. Meta-analyses confirm that cross-group friendships are particularly effective at reducing bias, including political and ideological extremism, by humanizing outgroups and challenging stereotypes.