The Causal Effect of an Intergroup Contact Intervention on Affective Polarization around Brexit: A Randomized Controlled Trial

With mounting evidence of the increase and harmful societal consequences of affective polarization, it is crucial to find ways of addressing it. This proof-of concept study tested the effects of a theory-based intervention on affective polarization in the context of Brexit. Sixty Leaver-Remainer dyads were randomized to engage in either a facilitated intergroup interaction or a control interaction, which was equivalent in structure and tone but was unrelated to Brexit identities. Different aspects of affective polarization were measured one month prior, immediately after, and one month after the intervention. Results indicate short-term intervention effects on intergroup affect and cognition, and willingness to compromise with the outgroup, but these mostly decayed over time. Evidence of selective attrition suggests that those with more extreme baseline opinions were more likely to drop out. The findings are of considerable importance for efforts to reduce affective polarization and highlight the challenge of engaging those who could benefit the most.