Moral Foundations and Political Orientation: Systematic Review and Meta-Analysis

We investigate the findings that liberals and conservatives rely on different moral foundations. We conducted a comprehensive literature search from major databases and other sources for primary studies that used the Moral Foundations Questionnaire and a typical measure of political orientation, a political self-placement item. We used a predefined process for independent extraction of effect sizes by two authors and ran both study-level and individual-level analyses. With 89 samples, 605 effect sizes, and 33,804 independent participants, in addition to 192,870 participants from the widely used YourMorals.org website, the basic differences about conservatives and liberals are supported. However, heterogeneity is moderate, and the results may be less generalizable than previously thought. The effect sizes obtained from the YourMorals.org data appear inflated compared to independent samples, which is partly related political interest and may be due to self-selection. The association of moral foundations to political orientation varies culturally (between regions and countries) and subculturally (between White and Black respondents an in response to political interest, but not in relation to other demographics). The associations also differ depending on the choice of the social or economic dimension and its labeling, supporting both the bidimensional model of political orientation and the findings that the dimensions are often strongly correlated. Oue findings have implications for interpreting published studies, as well as designing new ones where the political aspect of morality is relevant. The results are primarily limited by the homogeneity of the measures and included studies in terms of sample origins.