‘Seen one, seen ‘em all’: political outgroup homogeneity and negative affect

Outgroup homogeneity, the perception of lower trait variability in the outgroup, is an important psychological mechanism in intergroup relations. This concept is broadly applied to the context of political left-right party camps. A more homogenous perception of the outcamp limits perceived similarities and connections and could thereby foster negative impressions. This study examines whether the outcamp is generally perceived as more homogeneous than the incamp; whether this perception is driving negative affect; and lastly, if it reduces the likelihood of voting for the other camp. Support is found for all three assumptions using cross-sectional data from the full Comparative Study of Electoral Systems (CSES) and causal evidence from the German Longitudinal Election Study (GLES). Outgroup homogeneity emerges as a crucial aspect of political intergroup relations. It also provides context to findings on affective polarisation by identifying a form of outgroup dislike that is rooted in group identities, rather than factual disagreement.