Character  &  Context

The Science of Who We Are and How We Relate
Editors: Mark Leary, Shira Gabriel, Brett Pelham
Aug 10, 2020

Moral Offense or Stomachache? How Disgust Shapes our Moral Judgments

by Jessica L. Tracy
Young woman looking at smartphone with disgusted expression

Imagine that your best friend approaches you with a dilemma. He’s long been attracted to his sister, and he recently found out she feels the same. They’re thinking of having sex—fully protected and consensual, of course—and he needs your advice. I’m guessing that you’d have some sharp words for your friend as you tell him to rethink those plans, because sex with a sibling is just plain wrong; it’s not a morally acceptable action.

That response might make you a good friend, but why? Why do we find this kind of behavior so problematic? Is that judgment based on a rationally-derived principle about maximizing good and minimizing harm? Or, is it based simply on the fact that sibling sex makes you—and me—more than a little queasy? In other words, are our moral beliefs about incest—and maybe other “bad” behaviors—actually just gut feelings, literally stemming from our body’s tendency to become repulsed by certain human behaviors?

There are behaviors that many of us deem morally wrong and disgusting, including sex with a close relative. Touching a dead body and eating a deceased pet go in the same category. The more disgusting we find these behaviors, the more wrong they seem to be (first-cousin sex seems worse than second-cousin sex). Might our moral judgments, therefore, stem from the sickened way that morally improper behaviors make us feel?

Until recently, no research study had directly addressed this question. In fact, no study had determined whether, when we say we are “disgusted” by some morally reprehensible event, we mean it literally: we feel physically nauseated.  

This led my former graduate student, Conor Steckler, to come up with a brilliant idea. As people prone to motion sickness may know, ginger root is an antiemetic—it reduces nausea. Let’s give people ginger powder, Conor suggested, then ask them to weigh in on morally questionable scenarios—like peeing in a public pool or touching a corpse. If moral beliefs are driven by physical sensations of disgust, then reducing the nauseating physiological experience of disgust with ginger should reduce people’s judgments that something is immoral.

We spent hours filling hundreds of empty gel capsules with ginger powder (or sugar, for a comparison condition).  Neither our participants nor the research assistants who ran the study knew which pill each participant received. After taking their pills and waiting 40 minutes, participants were asked to read scenarios that described a range of possible moral infractions, such as someone peeing in a public pool, a morgue worker touching the eyeball of a corpse, a man buying an inflatable sex doll that looked like his receptionist, and a family cooking their recently-deceased dog for dinner. Then participants rated how morally wrong they believed each infraction was.

Sure enough, we found that participants who ingested ginger—which reduces physical nausea—decided that things like peeing in the public pool were not as wrong as did people who hadn’t ingested ginger. Blocking nausea changed our participants’ moral beliefs.

These effects did not emerge for every moral dilemma we presented. For infractions that a separate group of raters said were severe (like eating one’s own dog), ginger had no effect on judgments of morality. But for less severe infractions (like eating fully-sanitized feces, buying that inflatable sex doll, and, yes, peeing in the pool), people’s moral judgments were influenced by whether they got the pill that contained ginger. In cases such as these, in which people feel disgusted but don’t have a strong existing belief about whether the behavior is morally wrong, they lean on their gut emotions when making moral judgments. But, if people can instead think about the possibility of eating sanitized feces without wanting to throw up, the objectionable behavior seems less morally problematic.

Ginger also had no effect on people’s beliefs about moral violations that are based on feelings about what’s fair, or about the wrongness of harming others. For example, taking ginger did not make people think it is OK to drink and drive or to fail to tip a server. Rather, the violations that were affected by ginger centered on maintaining the purity of one’s own body. These transgressions are ones that, historically, have carried a high likelihood of transmitting disease. As a result, it is evolutionarily adaptive for us to feel disgusted by, and consequently to avoid, close contact with dead bodies, human feces, and certain unsafe sex practices. According to social psychologists Jonathan Haidt and Jesse Graham, in many cultures, this presumably adaptive tendency to avoid disease agents morphed into a broader ethic that uses concepts like purity, sanctity, and sin to discourage behaviors that are perceived to cause some manner of bodily degradation or uncleanliness.  

Yet in modern societies, the cultural norms that have made sanctity a moral issue have led to other problems. It is appropriate, and useful, to feel disgusted by spoiled foods, feces, and dead bodies. But that doesn’t mean we should moralize these emotional responses. We do not have to extend our beliefs about right and wrong to behaviors that don’t actually hurt other people, even if we find them disgusting. The tendency to do so is an ancient evolutionary holdover and, with the help of modern sanitation and safe sex practices, it’s one we can afford to set aside.

So, before deciding that something that cannot actually harm others is wrong, we might want to play it safe, and first reach for a ginger ale.

For Further Reading

This research was published in 2019 in the Journal of Personality and Social Psychology (Tracy, Steckler, & Heltzel, 2019). 

This blog is adapted from previously published in Aeon.

Jessica L. Tracy is a professor of psychology at the University of British Columbia and the author of Take Pride: Why the Deadliest Sin Holds the Secret to Human Success (2016)


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Why is this blog called Character & Context?

Everything that people think, feel, and do is affected by some combination of their personal characteristics and features of the social context they are in at the time. Character & Context explores the latest insights about human behavior from research in personality and social psychology, the scientific field that studies the causes of everyday behaviors.  

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