Abstract
Climate change presents a serious threat to the planet. Previous research reveals an ingroup–outgroup effect in support for climate policies, with greater support by U.S. participants for policies ostensibly endorsed by their own political party, despite acceptance of climate change among most Republicans and Democrats. We investigated moderation of this effect by the behavioral immune system (BIS), a suite of psychological mechanisms that cause individuals to avoid pathogens. This system has been linked to more negative responses to outgroup members. We extended previous research examining effects on group polarization to political polarization. We predicted that support for climate change policies would show stronger effects of own‐versus other‐party endorsement among people higher in BIS, as indexed by perceived vulnerability to disease (PVD). We found that the ingroup–outgroup endorsement effect on policy support was moderated by PVD. However, the effect was opposite to prediction. Whereas low PVD participants showed less support for climate policies endorsed by the other party than their own, high PVD participants supported climate policies regardless of endorser. This unexpected result may be construed as consistent with high PVD individuals feeling heightened vulnerability to environmental threats, which fosters support for protective policies, regardless of endorser. We also found less support for climate policies among Republican than Democrat low PVD participants, but no party effect among high PVD participants. This suggests that feeling vulnerable to environmental threats may lead Republicans to deviate from the party norm in their support for climate policies.