“…We recruited subjects from Amazon's Mechanical Turk, a survey platform whose subjects are known to fall short of demographically-representing the wider US population (Chandler & Shapiro, 2016). As highlighted in the introduction, Mason (2016Mason ( , 2018 finds that US party identity is increasingly in alignment with demographic identities (e.g., race, religiosity), and, importantly, that this alignment may serve to weaken barriers to out-party hostility (Mason & Wronski, 2018;Roccas & Brewer, 2002). For this reason, insofar as our subjects did not faithfully represent the demographic identities of the wider US population, it is possible that our analyses mis-estimated the population-level association between moral polarization and out-party hostility in IPD-MD.…”