Sunday, Jul 24, 2011 5:01 PM UTC

The science behind disgust

From dead bodies to pickles, the things that gross us out reveal a great deal about us. An expert explains

The science behind disgust

We all have things that disgust us irrationally, whether it be cockroaches or chitterlings or cotton balls. For me, it’s fruit soda. It started when I was 3; my mom offered me a can of Sunkist after inner ear surgery. Still woozy from the anesthesia, I gulped it down, and by the time we made it to the cashier, all of it managed to come back up. Although it is nearly 30 years later, just the smell of this “fun, sun and the beach” drink is enough to turn my stomach.

But what, exactly, happens when we feel disgust? As Daniel Kelly, an assistant professor of philosophy at Purdue University, explains in his new book, “Yuck!: The Nature and Moral Significance of Disgust,” it’s not just a physical sensation, it’s a powerful emotional warning sign. Although disgust initially helped keep us away from rotting food and contagious disease, the defense mechanism changed over time to effect the distance we keep from one another. When allowed to play a role in the creation of social policy, Kelly argues, disgust might actually cause more harm than good.

Salon spoke with Kelly about hiding the science behind disgust, why we’re captivated by things we find revolting, and how it can be a very dangerous thing. 

What exactly is disgust?

Simply speaking, disgust is the response we have to things we find repulsive. Some of the things that trigger disgust are innate, like the smell of sewage on a hot summer day. No one has to teach you to feel disgusted by garbage, you just are. Other things that are automatically disgusting are rotting food and visible cues of infection or illness. We have this base layer of core disgusting things, and a lot of them don’t seem like they’re learned.

But there’s also a whole set of things that have a lot of cultural and individual variation about whether it’s considered disgusting. For example, I like bloody steaks and my girlfriend, who is a vegetarian, finds them repulsive. The core base of what causes disgust has expanded to the point where certain kinds of moral violations, social transgressions, and even value systems of groups one is not a member of can come to be disgusting as well.

And that depends on where and how we grew up?

There’s a good case to be made that the culture we grow up in can fine-tune our disgust response or calibrate what we come to be disgusted by, but people don’t really need to learn how to be disgusted. The reaction is specified by nature, although it doesn’t start until we are around 3 or 4 years old. There’s also room for individual disparities. Maybe something traumatic happened to you as a child and Raggedy Ann dolls make you feel disgusted. That is a personal idiosyncrasy.

So what actually happens when we feel disgusted?

There are different elements of the response that are psychologically bound together, and they all tend to happen when you feel disgusted by something. The one that’s probably the most recognizable is what I call the “yuck face” — your nose and brow wrinkles and you might stick out your tongue — which mimics the facial movements that precede actual retching. When you’re disgusted, you make that face to signal what you’re feeling to other people.

But because disgust is an emotion, it’s not purely cognitive or psychological. There are physiological elements that accompany it, too. Unlike other emotions, like fear and anger, which make your heartbeat speed up, disgust makes your heartbeat slow down a bit. There is also a little flash of nausea or the sense of something being wrong with your stomach. This happens because the aversion that’s produced with disgust uses a lot of the same physiological elements that make up the digestive system.

How do we know when we’re truly disgusted by something, as opposed to merely disliking it?

You have this quick, reflex-like tendency to move away from whatever you find disgusting. You might not actually move, but you’ll have this flash of motivation to jerk away from it. Some of the really interesting things about disgust are the more psychological components of it. When you’re disgusted by something, it captures your attention. It seems offensive and tainted in some way, and we think about disgusting things as though they have the ability to contaminate other things. So, if something we find disgusting touches another object, that object becomes disgusting as well. We track where the property of disgust is in the world, and that tendency seems to be automatic.

It makes sense that disgust would help us to avoid things that may be risky.

Disgust initially evolved to protect us from contagious diseases. We have a lot of different ways to protect us from infection. Internally we have an immune system with antibodies. One way to think of our skin is as a barrier that keeps things out that might damage us. Disgust is a psychological component to this arsenal of protective weaponry. Instead of waiting until something gets into our system that we have to fight to push out, disgust helps us to stay away from objects and people that are likely to get us sick.

But if disgust is supposed to help us avoid consuming things that are bad for us, like unhealthy foods, why are our rates of obesity going up?

When it comes to the food side of disgust, the things we are typically disgusted by would be like poison to eat and have an immediate adverse impact, like rotting meat or moldy bread. Someone might find Big Macs nasty, and in the long run eating them might contribute to bodily damage, but eating a Big Mac usually won’t make you violently ill in the next couple of hours. If it did, we wouldn’t eat them. Disgust is a crude psychological tool that helps us sort what to eat from what not to eat, but there are also powerful cultural forces that help to suppress it.

At some point, humans started to get disgusted by the way other people behave. Why did that happen?

Humans are evolved creatures, but we’re also spectacularly different from most other creatures in the natural world. Humans went down unique evolutionary pathways when we were evolving, and part of what happened was that we became more reliant on culture. When some new issue comes up, Mother Nature doesn’t start from scratch; she tinkers with what already exists. When people began to get more social and more reliant on cultural information, some problems came up. So Mother Nature did her tinkering thing and made disgust one of the mechanisms to help regulate social interactions.

Are any social behaviors universally disgusting?

The best candidates for universal disgust solicitors are the ones that are closely linked to food and infection, but it looks like there may be themes on a social or moral level. Certain forms of deviant sex are considered disgusting, but what counts as deviant varies greatly from culture to culture. Sexual activity is the sort of thing that is more likely to get disgust brought to bear on it, but I’ve found a lot of different variations on that theme.

American popular culture seems to be captivated by things our culture finds disgusting. Why are we so drawn to “Saw” films and reality TV like “Fear Factor”?

People have asked me questions like this before, and from the point of view of my research, I don’t really know. The one thing I can say is that something you find disgusting will definitely capture your attention because we’re quite sensitized to them. Beyond simply having the ability to draw our attention, we tend to tell other people about things that are disgusting. Maybe this is a really cheap pandering to the audience that plays on these propensities we have.

Do we have the ability to change the things we feel disgusted by?

People don’t exactly know how this works, but acute exposure to something can have the effect of decreasing our feeling of disgust toward it. For example, if you go to medical school, you have to deal with corpses a lot because you’re learning human anatomy. As a result, your sensitivity to death-related solicitors [i.e. things] drops off a little. The key part of this, however, is that it is only for death-related disgust solicitors that the sensitivity decreases. Another example is that over time, mothers become less disgusted by the dirty diapers of their own child, but they remain disgusted by the dirty diapers of other peoples’ children. But what’s happening there isn’t conscious. It’s automatic. In general, there’s not a lot known about the ways we can deliberately or voluntarily make ourselves not be disgusted by things.

Do you think shows like “Bizarre Foods” can subconsciously help us to overcome some of our disgust of other cultures, like the fact that Cambodian people eat spiders?

It’s an interesting suggestion. Shows where people eat extremely outlandish foods from other cultures that Americans might find disgusting could be a way of familiarizing ourselves with something so it doesn’t seem so outlandish. It’s pure speculation, but familiarizing ourselves with things that are common in other cultures may be a way to fight the dehumanizing and xenophobic tendencies that come with feelings of disgust.

What about our friends and family? Can they teach us to stop being disgusted by something?

You would think that our peers have a lot of influence on what we find disgusting and what we don’t, but past a certain point, they may be fixed. Let’s say you grow up in the Midwest like I did, and you go to state fairs where you eat elephant ears and fried Twinkies. Then as an adult, you move to San Francisco where you hang out with people who find state fair food revolting. Can their social influence make you disgusted by the foods you used to love as a kid? I tend to think you can make an effort to present as though you’re disgusted by something or aren’t, but I don’t know that you can ever actually fully change your sensibilities once they get calibrated.

So someone might tell their friends they hate fried Twinkies then stuff their face with them when they visit their family in Indiana?

Exactly. You present one face to your coastal friends and another to your friends and family back home. But whether that gets down into the deeper psychological machinery isn’t something I know yet.

Can disgust be dangerous?

It’s an indisputable fact at this point that disgust influences a lot of social and moral judgments in a variety of ways. An interesting question is whether or not feelings of disgust should play a part in deliberate decision making. If a large percentage of the population finds some social practice disgusting — like stem cell research or cloning — is that a good reason to think the practice is immoral? I argue that it should not. A practice people are disgusted by may or may not be immoral, but the fact that people are disgusted by it is totally irrelevant to that particular question. We shouldn’t trust disgust to give us reliable information about morality. We know the story of how it evolved and why it varies from one culture to the next. Investing the emotion with moral authority is extremely dubious, and we shouldn’t uncritically trust it.

Does disgust play a role in creating social inequality? So gays and lesbians shouldn’t be denied the right to marry on the grounds that their so-called disgusting lifestyle undermines the sanctity of marriage?

The groups that are most likely to elicit disgust are often the lowest on the social hierarchy. Women have been made into objects of disgust a lot throughout history. Disgust can be a very powerful rhetorical tool to discredit, undermine or demonize an opponent or a group of people with whom you don’t agree. An easy way to do those things is to portray someone as infecting the integrity of your own social group. Disgust is a really potent emotion, and using it can be pretty rousing and effective because it has an almost subliminal influence on how we think of things.

Why not use it to make discrimination unfashionable?

I argue against disgust ever being used as a social tool, even to get rid of something we all logically agree is morally pernicious. It’s easy to imagine someone arguing that, since rational and calculated arguments haven’t done a lot to change public opinion about racism, maybe we should try portraying racism and racists as disgusting. The powerful influence of this emotion might help push racism to the edge of society or eliminate it altogether, but my response is that we still shouldn’t do it. It’s not ethically appropriate to deliberately depict any group of people as disgusting because disgust makes it very easy to dehumanize, and that would do the very thing we seek to undo.