'Us versus Them': What Drives Political Polarisation

Political polarisation is often caused by misinformation, echo chambers, or partisan media coverage. However, a new study by Frederik Schwerter, Nicola Gennaioli and Guido Tabellini suggests that political divisions can deepen even in the absence of substantial information or deliberate attempts at persuasion. Simply drawing attention to social conflicts can shape political beliefs and even alter people's perceptions of factual questions. 

The study is based on a pre-registration online experiment involving nearly 13,000 participants drawn from a representative sample of the US population. Before answering questions on political issues, some participants were asked to think about a social group they perceived as a threat. They were then asked about topics including income inequality, immigration, the role of government in income redistribution, and abortion. For another group of participants, the researchers made just one small change: they altered the order of questions, asking participants about topics first and then to reflect on a “threatening” social group.

Despite this minimal change, the results were striking. Depending on the topic, disagreement between groups increased by 8 to 35 per cent when a social outgroup was mentioned first. Although participants received no additional information, both their political views and their perceptions of factual questions shifted. The strongest effects were observed on issues where disagreements between groups were already greatest. 

The authors explain these findings through social identity theory. People identify with multiple economic, political and cultural groups at the same time. When a particular social conflict becomes more salient, individuals are more likely to interpret political issues through the perspective of their own group. As a result, their beliefs become more closely aligned with those of their in-group, even when assessing factual questions. 

The researchers also found that different types of social conflict influence beliefs in different ways. Participants whose economic and cultural views did not fully align-for example, those who were economically progressive but culturally conservative-responded differently depending on whether economic or cultural conflicts were made more salient. This suggests that political attitudes are not fixed but can shift according to which social divisions are most prominent at a given moment. 

Importantly, these effects are not limited to party affiliations. Politically independent respondents also became more polarised when social conflicts were made more salient. This indicates that social identities influence political beliefs independently of traditional party loyalties. 

The findings have important implications for politics and the media. They suggest that political polarisation is not driven solely by misinformation or biased reporting. The choice of which social conflicts politicians, the media and social media platforms repeatedly highlight can itself activate social identities and shape political beliefs. 

Overall, the study demonstrates that political polarisation does not necessarily require additional information or misinformation. Simply drawing attention to social conflicts may be enough to shape political beliefs and perceptions of factual questions.