His Moral Foundations Theory looks at the way morality varies between cultures and identifies five fundamental moral values shared to a greater or lesser degree by different societies and individuals. These are:
- Care for others, protecting them from harm. (He also referred to this dimension as Harm.)
- Fairness, Justice, treating others equally.
- Loyalty to your group, family, nation. (He also referred to this dimension as Ingroup.)
- Respect for tradition and legitimate authority. (He also referred to this dimension as Authority.)
- Purity, avoiding disgusting things, foods, actions.
Haidt found that Americans who identified as liberal tend to value care and fairness considerably higher than loyalty, respect, and purity. Self-identified conservative Americans value all five values more equally, though at a lower level than the liberal concern for care and fairness. Both groups gave care the highest over-all weighting, but conservatives valued fairness the lowest, whereas liberals valued purity the lowest. Similar results were found across the political spectrum in other countries.