The Human Brain

The Human Brain

Wednesday, December 17, 2008

Yuck! More Evidence that Disgust Influences Our Moral Judgments

Disgust is an emotion that has evolved to protect us from ingesting toxins that could be potentially harmful to our survival and ultimately, to our ability to pass on our genes. Charles Darwin (1872) described disgust as “something revolting, primarily in relation to the sense of taste as actually perceived or vividly imagined” (p. 253). As demonstrated by Paul Ekman’s research, disgust is a cross-cultural human emotion. Humans in all cultures recognize the distinctive facial expression of the wrinkled nose, curled lips and protruding tongue as a reaction to disgusting stimuli.

Although the emotion of disgust has evolved to protect us from the consumption of harmful toxins, it is also intimately involved in our moral decision-making. Haidt (2000) proposed an intuitional model of moral judgments. His model suggests that our moral decisions are based on automatic, emotional reactions rather than conscious reasoning. According to his model, moral reasoning provides us with a post hoc rationalization for our moral judgments rather than the moral judgment itself.

The automatic emotions that influence our moral judgments are referred to as moral emotions. They include emotions such as anger, disgust, embarrassment, empathy etc. Rozin and Haidt (2000) extended the definition of disgust to include disgust moral offenses. In support of their new definition of disgust, Rozin and colleagues (1997) found that moral vegetarians are more disgusted by meat than health vegetarians. Recent research has also suggested that sensitivity to disgust is related to ethnocentrism (Navarrete & Fessler, 2006) as well as various politically conservative issues including abortion, immigration, homosexual marriage and stem-cell research, as well as prejudice toward homosexuals (Terrizzi & Ventis, 2006; Inbar, Pizarro, Knobe & Bloom, 2008). Disgust sensitivity has also been found to be correlated with other variables such as right-wing authoritarianism, religious fundamentalism (Terrizzi & Ventis, 2006) and religious obsessions (Olatunji, Tolin, Huppert & Lohr, 2005).

More recently Schnall and Colleagues (2008) conducted a series of four experiments in which they manipulated disgust using “fart spray”, making the lab dirty (stained and stick desk, chewed pen, pizza boxes, etc.), recalling disgusting experiences and showing disgusting video footage. The results of their first study indicated that the participants who were exposed to the “fart spray” had more severe moral reactions to first cousins marrying and having sex. In the remaining studies, the researchers found that disgust only influenced the moral judgments of those who exhibited high levels of private body consciousness.

Our moral judgments may not be as rational as we like to think that they are. Research is beginning to reveal that our behavior and decision-making is often determined by automatic, emotive processes, which have evolved to ease our decision-making in order to make it easier for us to function adaptively in our social worlds. The evidence here suggests that disgust is one of those emotions that can influence our moral decision-making. Disgust, which is an emotion that has evolved to protect us from consuming potentially harmful substances, can be co-opted by our moral decision-making processes to make decisions about moral issues.

Darwin, C. (1872). The expression of emotion in man and animals. Chicago: University of Chicago Press.

Haidt, J. (2001). The emotional dog and its rational tail: A social intuitionist approach to moral judgment. Psychological Review, 108(4), 814-834.

Inbar, Y., Pizarro, D., Knobe, J., & Bloom, P. (2008). Disgust sensitivity predicts intuitive disapproval of gays. Manuscript submitted for publication.

Navarrete, C. D., & Fessler, D. M. T. (2006). Disease avoidance and ethnocentrism: The effects of disease vulnerability and disgust sensitivity on intergroup attitudes. Evolution and Human Behavior, 27(4), 270-282.

Olatunji, B. O., Tolin, D. F.; Huppert, J. D. & Lohr, J. M. (2005). The relation between fearfulness, disgust sensitivity and religious obsessions in a non-clinical sample. Personality and Individual Differences, 38(4), 891-902.

Rozin, P., Haidt, J., McCauley, C., & Imada, S. (1997). Disgust: Preadaptation and the cultural evolution of a food-based emotion. In H. MacBeth (Ed.) Food preferences and taste. Providence: Berghahn Books, 65-82.

Rozin, P., Haidt, J., & McCauley, C. R. (2000). Disgust. In M. Lewis & J. M. Haviland-Jones (Eds.), Handbook of emotions, 2nd Edition (pp. 637-653) New York: Guilford Press.

Schnall, S., Haidt, J., Clore, G., & Jordan, A. (2008). Disgust as embodied moral judgment. Personality and Social Psychology Bulletin, 34(8), 1096-1109.

Terrizzi, J., & Ventis, L. (2007, May). Prejudicial attitudes toward homosexuals: The competing roles of moral reasoning and the moral emotion of disgust. Presented as a talk at the annual meeting for the Human Behavior and Evolution Society, Williamsburg, VA.