Liberals and conservatives currently struggle to reach political agreement on policy proposals. While political polarization is closely associated with this phenomenon, the precise psychological mechanisms via which polarization works to affect political compromise remain to be fully explored. Across five studies (N = 1236; 2126 total individual observations), we uncover one such mechanism by exploring a novel and robust bias that emerges at the crossroads of policy trade-offs and partisanship. We call it the Partisan Trade-off Bias. When interpreting policy trade-offs, both Democrats and Republicans view the unintended but unavoidable side effects of policies proposed by contrapartisans as wanted and intended. Yet they do not attribute intentionality to the very same types of side effects of policies proposed by copartisans. We provide evidence for this bias across four types of policy trade-offs, including taxes, environmental regulation, gun control, and voting rights. Importantly, we show that the partisan trade-off bias is a unique contributor to decreased willingness to accept policy deals from contrapartisans, thus reducing the chances of reaching political agreement. Our studies suggest that the partisan trade-off bias is a product of the lack of trust in contrapartisans. In an experimental study, we manipulate trust and decrease the magnitude of this bias, showing evidence for our proposed mechanism and revealing a potential intervention to foster political compromise.

自由派和保守派目前很难就政策建议达成政治共识。虽然政治两极分化与这种现象密切相关，但两极分化影响政治妥协的确切心理机制仍有待充分探索。在五项研究中（N  = 1236；总共 2126 个个体观察），我们通过探索在政策权衡和党派之争的十字路口出现的一种新颖而强大的偏见，发现了一种这样的机制。我们称之为党派权衡偏见. 在解释政策权衡时，民主党人和共和党人都将反对党提出的政策的意外但不可避免的副作用视为想要和有意的。然而，他们并未将意向性归因于同党提出的政策的相同类型的副作用。我们在四种类型的政策权衡中提供了这种偏见的证据，包括税收、环境监管、枪支管制和投票权。重要的是，我们表明，党派权衡偏见是导致接受反对派人士的政策交易意愿下降的独特因素，从而降低了达成政治协议的机会。我们的研究表明，党派权衡偏见是对党派人士缺乏信任的产物。在一项实验研究中，我们操纵信任并降低这种偏见的程度，