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.

Why Does Disgust Induction Cause Conservatives to Become More Prejudice but Liberals Less Prejudice?

For the purposes of this post, I am going to refer to high authoritarians as conservatives and low authoritarians as liberals. I have two reasons for doing this: 1. Political conservatism is strongly correlated with right-wing authoritarianism and 2. Liberal and conservative are terms that are more manageable and easily understood.
There are many possible reasons why conservatives and liberals react differently to disgust induction. Haidt’s research suggests that liberals and conservatives differ in regard to their moral emotions. In other words, conservatives and liberals base their moral judgments on different emotions. For example, liberals are more sensitive to empathy whereas conservatives are more sensitive to disgust.
One possible reason why conservatives become more prejudice when disgusted may be because they are more sensitive to disgust. But this does not help explain why liberals become less prejudice when they are disgusted.
It is possible that liberals are averse to prejudice. The aversive racism literature suggests that people avoid expressing prejudicial attitudes so they are not seen as bigots. Thus, liberals are disgusted at the prospect of being prejudice whereas conservatives are disgusted by homosexuality.
Disgust is an emotion that originally evolved to avoid oral ingestion of contaminants as Darwin suggested in The Expression of Emotions in Man and Animals. More recently, Haidt and colleagues have indicated that morally repugnant acts can induce disgust. My hunch is that evolution designed the emotion of disgust as a general mechanism for the avoidance of undesirable stimuli but our culture is what tweaks the knobs.
More research needs to be done to confirm this hypothesis.

More Evidence for the Role of Moral Emotions in the Formation of Moral Judgments

I recently posted some of the findings from my thesis, which suggests that moral emotions are more predictive of moral judgments than moral reasoning. Specifically, people who are high in disgust sensitivity and high in moral development are just as prejudice toward homosexuals as those who are low in moral reasoning, which indicates that disgust can overwhelm our ability to reason.

In the second study of my thesis, I found that inducing disgust can make certain individuals more prejudice toward homosexuals while making other individuals report less prejudice.

Participants in this study were asked to read one of two scenarios and write a brief paragraph describing their physical and emotional reactions. Half of the participants imagined what it would be like to consume a bowl of maggots and the other half described what it would be like to eat a bowl of lettuce.

Following the experimental manipulation, the participants completed measures of prejudice toward homosexuals, disgust sensitivity, and authoritarianism. Authoritarianism was measured using the right-wing authoritarianism scale, which assess conventionalism, authoritarian submission, and aggression toward out-groups. Traditionally, individuals who score high on the right-wing authoritarianism scale are more likely to be prejudice toward homosexuals, minorities, and more likely to be politically conservative.

Disgust induction for individuals who scored high on the authoritarianism scale resulted in an increase in prejudicial attitudes toward homosexuals as compared to those in the control group. In addition, disgust induction for those who scored low on the authoritarianism scale led to a decrease in prejudicial attitudes toward homosexuals as compared to those in the control group.

These results demonstrate that conservatives and liberals are differentially affected by the moral emotion of disgust.

Moral Emotions vs. Moral Reasoning

Psychologist are currently debating the underlying processes involved in our moral judgments. Some psychologists believe that our moral judgments are caused by automatic unconscious moral intuitions whereas others believe they are due to conscious reasoning and reflection.

Traditionally, psychologists subscribed to the rationalist perspective. Rationalist proponents have included Jean Piaget, Lawrence Kohlberg, and James Rest. According to their perspective, moral reasoning follows a cognitive-developmental trajectory in which individuals progress from basing their moral judgments on selfish issues early in development to basing them on universal ethical principles later in development.

More recent evidence, however, suggests that moral judgments may result from quick, automatic flashes of emotion. The intuitionist perspective assumes that moral reasoning serves as a post hoc rationalization rather than a cause of moral judgments.

In support of the intuitionis perspective, Jonathan Haidt found that when participants were asked to imagine a scenario in which a brother and sister have a sexual encounter, participants invariably label the behavior as morally wrong. However, they have a difficult time explaining why they find immoral. Participants often cite the danger of inbreeding and the emotional damage that could be caused by the sexual encounter. When the researcher reminds them that the brother and sister used two forms of protection and neither of them was emotionally affected by the encounter, the participants respond by saying something like “I don’t know, I can’t explain it. I just know it is wrong.”

So if it is not moral reasoning that causes our moral judgements, what is it? Haidt suggest that it is our moral emotions. These emotions include empathy, guilt, embarassment, anger, disgust, etc.

In a recent attempt to determine whether moral reasoning or moral emotions played a bigger role in predicting moral judgments, my advisor and I examined the roles of moral reasoning and the moral emotion of disgust in predicting individuals' attitudes toward homosexuality.

We found that individuals who were high in moral reasoning were less likely to hold prejudicial attitudes toward homosexuals and that individuals who were sensitive to disgust were more likely to exhibit prejudicial attitudes toward homosexuals.

More importantly, our results showed that the moral emotion of disgust overwhelms moral reasoning such that individuals who are high in both moral reasoning and disgust ressemble those who are low in moral reasoning in regard to their prejudicial attitudes toward homosexuals.

Additionally, people who were high in disgust were more likely to be anti-abortion, more likely to want a stricter immigration policy, more likely to support the war in Iraq, and less likely to support terminal patients' right to die.

In his book, The Expression of the Emotions in Man and Animals, Darwin (1872) refers to disgust as “something revolting, primarily in relation to the sense of taste, as actually perceived or vividly imagined." Although, the emotion of disgust evolved for the purpose of avoiding oral contamination. The evidence presented here suggests that it also serves a secondary as one of our moral emotions.

Click here and learn more about the moral emotions.