When we think about ethics and morality, we often think that it is rational. Morality requires making judgments of right and wrong, and making judgments about what is right and wrong is a matter of logic and reasoning. But researchers interested in the psychology of morality are finding that morality is much more embodied and affective than we’d like to think. Specifically, moral judgments have been found to be linked to the feeling of disgust.

Schnall, Haidt, Clore, and Jordan (2008) hypothesized that morality may be more of a gut reaction that is later justified by moral reasoning: “moral reasoning is an important part of moral life, but for most people, most of the time, most of the action is in the quick, automatic, affective evaluations they make of people and events.” (p. 1097) They tested this hypothesis in a series of awesome studies that included fart spray and dried up smoothies. (You have to acknowledge how incredibly cool it is that “fart spray” made it into a top tier psychology journal.)

The researchers asked participants to read and think about several vignettes concerning moral judgments. These vignettes ranged from personal (e.g., whether sex between first cousins is ok, whether it is wrong for someone to falsify their resume) to public (e.g., whether participants would support nondenominational school prayer, whether participants would support spending more of the state’s money for waste treatment); some of them were disgusting (e.g., eating dead dog) while others were not meant to elicit disgust (e.g., stealing). Here is the cool part: the researchers experimentally manipulated the level of disgust that participants would feel. In one study, some of the participants completed the questionnaire in a room that smelled like fart (yes, the experimenters secretly sprayed fart spray into the air), and in another study, they had to complete the questionnaire with a pen that someone had chewed up, while sitting at a table with a cup of old, dried up smoothie and some used tissues, in a chair with a dirty, worn out cushion, in a room where the trash can overflowed. (Folks in the no-disgust condition completed their questionnaires in clean, tidy rooms.) 

Compared to participants who did not experience disgust, the participants who smelled fart in the room or sat at the table with the gross old food made more severe moral judgments regardless of whether the vignettes were themselves disgusting or not. In addition, this effect was most pronounced for participants who were sensitive to their own bodily sensations (e.g., people who were sensitive to changes in their bodily state), was unrelated to negative feelings (like sadness), and was observed only moral (not non-moral) judgments.

The authors interpreted these results as evidence of “a causal relationship between feelings of physical disgust and moral condemnation”, “an affective basis for judgments”, and that “disgust influenced judgments of non-disgusting moral violations as much as it influenced judgments of disgusting moral violations” (p. 1105-1106). We use our affect and bodily states as information, and in this study, participants used their feelings of disgust as information about whether something was morally right or wrong. So if you think your moral judgments are completely rational, reasonable, and logical, think (or smell) again!

If you are interested in reading this study you can download it from Jon Haidt’s homepage (it’s item#54).