Liberals and conservatives rely on different sets of moral foundations.

TLDR

Moral judgments differ across the political spectrum, raising questions about the underlying mechanisms. The study aimed to test moral foundations theory by developing measures of the five moral intuitions. The authors created multiple methods to assess Harm/care, Fairness/reciprocity, Ingroup/loyalty, Authority/respect, and Purity/sanctity. Across four studies, liberals consistently endorsed Harm/care and Fairness more than the other foundations, whereas conservatives used all five foundations more equally, highlighting persistent moral disagreements in the American culture war.

Abstract

How and why do moral judgments vary across the political spectrum? To test moral foundations theory (J. Haidt & J. Graham, 2007; J. Haidt & C. Joseph, 2004), the authors developed several ways to measure people's use of 5 sets of moral intuitions: Harm/care, Fairness/reciprocity, Ingroup/loyalty, Authority/respect, and Purity/sanctity. Across 4 studies using multiple methods, liberals consistently showed greater endorsement and use of the Harm/care and Fairness/reciprocity foundations compared to the other 3 foundations, whereas conservatives endorsed and used the 5 foundations more equally. This difference was observed in abstract assessments of the moral relevance of foundation-related concerns such as violence or loyalty (Study 1), moral judgments of statements and scenarios (Study 2), "sacredness" reactions to taboo trade-offs (Study 3), and use of foundation-related words in the moral texts of religious sermons (Study 4). These findings help to illuminate the nature and intractability of moral disagreements in the American "culture war."