The Science (and History) of Disgust: Interview with Psychologist Rachel Herz on Understanding Human Repulsion



Robin Lindley is a Seattle writer and attorney. He contributes interviews and other writing to the History News Network, Crosscut, Real Change and other publications on history, medicine and science, politics, justice, the media and the arts.

Only humans experience disgust, an emotion that evolved initially to help us avoid toxic food and disease and morphed into a manipulable sense that infuses personal choices about cuisine and friends and sex partners as well as cultural decisions on economics, law, moral codes, politics, and allies and enemies.

Whether something is disgusting varies from place to place and over history. In the 1600s, for example, New Englanders found lobster so foul that laws were enacted to bar slave owners from serving it to slaves more than three days a week -- yet now most people consider lobster a delicacy.

In her latest book, That's Disgusting: Unraveling the Mysteries of Repulsion (W.W. Norton & Co), Dr. Rachel Herz -- a psychologist, cognitive neuroscientist and expert on the sense of smell -- explores this fascinating emotion and how it permeates so many important aspects of our lives. She differentiates disgust, our most egoistic and individualized emotion, from our other relatively outward-focused, automatic emotions of happiness, sadness, anger, fear and surprise.

That’s Disgusting offers a journey through the vile and disgusting from fetid food and vomit, blood, urine, and feces to pornography, horror movies, disease, cannibalism, and the fear behind it all, death. Dr. Herz relies on recent psychological and medical studies to explain how the brain interprets disgust and how disgust affects human behavior. And she points out how leaders have manipulated disgust to vilify and isolate particular groups such as what happened with the Tutsis in Rwanda in 1994, the Jews in Nazi Germany, and immigrants today.

Dr. Rachel Herz grew up in Montreal Canada and received her PhD from the University of Toronto. She is on the faculty of Brown University and also works as a professional consultant. She has studied the psychology of smell, emotion and cognition since 1990 and has written dozens of academic articles on human emotion and smell as well as a critically acclaimed 2007 book, The Scent of Desire: Discovering Our Enigmatic Sense of Smell (William Morrow/Harper-Collins). In her research studies, she uses psychophysical, self-report, cognitive-behavioral and neurological techniques, including functional magnetic resonance imaging (fMRI).

Dr. Herz also serves on several advisory boards, including The Fragrance Foundation, and consults for many of the world's leading flavor and fragrance companies.

Dr. Herz recently spoke extensively by telephone about That’s Disgusting and her other research from her office in New England.


How did you come to write about disgust now?

It came from two directions. The first was a joke because my first book, The Scent of Desire, was about the psychology of smell. After writing that book, I got a lot more media attention, and the National Rotten Sneakers Contest contacted me and asked if I’d be a judge for it. The contest was explained to me. Kids would come together from all around the country after their regional stink-offs, and the contest was for the smelliest sneakers of all. It sounded like fun. It was held in Montpelier, Vermont, and I was being offered a hotel room at a resort in Stowe so I said “okay.” This contest is actually in The Farmers’ Almanac, so it is well known. When I told people about it they couldn’t believe I had agreed to do it, and kept pointing out to me how disgusting it was going to be.

Two things then happened. One, I made a joke that I was doing it for research for my next book, The Scent of Disgust. That set the ball rolling in my mind that maybe disgust was an interesting topic, and I had been looking for a topic for my next book. But also, thinking about what I was going to deal with in the contest influenced how I responded to the sneakers [and] when I had to come nose to nose with them I discovered it wasn’t nearly as bad as I thought it was going to be. I had imagined the most excruciating smells possible, and when I got down to actually smelling the odors were tolerable by comparison. This started me to think about how cognitively and psychologically manipulable disgust is, and how it has a lot of fundamental commonalities with the sense of smell, which is also very psychologically manipulable, contextual, and meaning dependent, and I began to think more deeply about disgust as a viable topic.

In fact, long before this contest, when I started my faculty career, I became intellectually interested in disgust. I was at the Monell Chemical Senses Center in Philadelphia, an institute devoted to smell and taste research affiliated with the University of Pennsylvania, and I met Paul Rozin in the psychology department at Penn, he is the leading [expert] on disgust, and he was also interested in taste. I participated in his group seminars. He first got me intrigued with disgust when he talked with me about his research. So for a long time I had a percolating interest, but never expected to put it all together.

You write about the evolution of disgust and how it’s an emotion that has contributed to human survival through history.

Disgust is a very interesting emotion. It contributes to our survival by helping us avoid eating poisons and catching diseases. But it’s also something which, from a historical perspective, has been put to terrible use in terms of maligning groups of people, inciting genocide, and influencing our response to the “other,” whether foreigners or immigrants and so forth.

The manipulation of disgust at a political level has been extraordinarily damaging if not outright entirely destructive to whole groups of people. Even though it’s an emotion that helps us, it’s also an emotion that destroys us. More important, it’s an emotion that needs to be learned. We don’t automatically know what we need to be disgusted by. We need to learn it, and we learn it from our culture and it’s very manipulable and can be influenced by all sorts of things.

The disease-vector connection historically has been the most powerful and negative in creating an annihilation-extermination response towards groups of people. For example, calling a group of people “cancerous tumors” or calling them “vermin” as was done in World War II with Nazi propaganda against Jews and in the genocide of Tutsis in Rwanda. In fact, recently in the news, the UN ambassador from Iran called Israel a “cancerous tumor.” That’s directly out of the playbook of the Nazi propaganda machine. When you do that, people have a disgust response, which they have learned, to disease and vermin. As soon as we castigate a group of people as having those qualities, those people become contaminated and viewed as subhuman vermin and diseased—things that we want to eradicate, to exterminate. It’s very dangerous.

You’d think we wouldn’t be so susceptible as rational people but it is actually very easy to manipulate. In a recent experiment, it was shown that college students think about drug addicts and the homeless as subhuman and disgusting. The “human focused” part of the brain is literally turned off when looking at pictures of people in these groups. They are subhuman in the students’ minds and literally no different from an overflowing toilet in terms of the kind of disgust and aversion they elicit, whereas other downtrodden groups, such as people with disabilities, elicit a certain degree of human pity so that, although they may perceived as disgusting, they are not perceived as nonhuman.

A very dangerous thing happens when you turn somebody into some thing, and that’s where the destructiveness takes place.

It’s amazing how quickly that sense of disgust can take hold.

It’s called the instinct that has to be learned. It feels like an instinct when we experience disgust. When you look at an earthworm or step in poop or have to shake hands with a sweaty, coughing stranger, it feels like disgust comes on automatically out, but had you not learned what to be disgusted by and how to be disgusted, you wouldn’t have that response. For example, there are feral children who have been brought up without any socialization whatsoever, and they do not appear to show any disgust. The same with young children prior to being socialized. And there are certain individuals who, because of neurological abnormalities, also do not recognize or experience disgust. It’s particularly interesting to me that psychopaths don’t experience disgust, because they are also the classic anti-social personality. It turns out that disgust is an extremely social emotion.

Do you think Americans view poverty and homelessness with a collective kind of disgust? It seems that American society tends to put things we don’t like to see out of sight, out of mind, such as mental illness and homelessness, and we fight wars at a great distance.

We live in a world in North America where we have the privilege of being able to sanitize our environment to a fairly high degree, and we do this at several levels. We also clean our bodies excessively compared to the rest of the world. And we clean up our streets by hustling homeless people into shelters so other people won’t see them much more than is done in Europe or the rest of the world. It’s interesting how we sanitize our bodies and our environments.

This also happens with mental illness, but I think fortunately this is changing (with respect to mental illness). But it’s still the case that when people are told that the last people who swam in a pool were mental patients, they don’t want to swim in the pool.

We’re very easily affected by a kind of magical contagion. For example, the repulsion we have at the concept of mental illness creates the feeling of magical contamination, and so we don’t want to touch or be immersed in something that is connected to our aversion. Even though we know logically that we can’t put something in the water to cause or catch mental illness, we still somehow feel it could rub off on us.

And you write about the disgust evoked by the idea of wearing a sweater that was supposedly worn by Hitler or buying a bag of cookies that is placed in a shopping cart with a sealed package of feminine hygiene products.

That’s very interesting to me. Menstrual blood is deemed the worst blood in the world, and much worse -- depending on the culture -- than any other bodily fluid that comes out of humans. That’s shocking to me. It is the signifier of being able to produce life, so there’s a strange paradox about why it would be so disgusting. Menstruation is indicative of a fertile female and the concept of procreation is the basis for everything, and yet menstrual blood is viewed as this repulsive signal.

Women also have a long history of being [seen as] illness-producing and contaminating. The same kind of language that has been used against Jews has also been used against women.

I was blown away by the amount of misogyny there has been historically and how disgust has been used to make women more repulsive. It’s interesting how feminine attributes have been disgustified: soft and moist and other qualities that are perceived as disgusting compared to the smooth, strong and sleek male body.

As you suggest, women -- like lepers -- have often been isolated through history because of a sense they’re diseased.

That has been a longstanding trajectory through cultural history with the idea that women could cause sickness by menstruation. In the nineteenth century, doctors said women shouldn’t be around food while menstruating because they could literally spoil the food by their contact with it as a function of menstruating, which is so nonsensical that it boggles the mind, yet it was taken seriously and stated by medical practitioners. I can’t imagine the folkloric anecdote that was used to justify this belief because it sounds so absurd to me. It’s interesting too that [menstruation] is viewed as something women should be ashamed of and women should not have sex when menstruating, and many women unfortunately hold this attitude. Many men and women in our culture now don’t care if the woman is menstruating while having sex, but there are still both men and women who view this as disgusting. And many women have internalized this shame and disgust about their bodies and how they shouldn’t be touched during this time.

You write also of pornography and disgust. In the images of nudes in men’s magazines like Playboy, pubic hair was airbrushed out in the fifties and sixties, and then appeared in the seventies. Has our sensitivity changed?

There’s been a big upswing in what we’re exposed to in terms of sexuality and much more so with gore. It’s much more acceptable to show extreme gore than even mild sexuality.

In the seventies and eighties, magazines like Playboy showed women’s bodies with pubic hair, and now the fashion is in fact to have no or almost no pubic hair. Although they show the full body, the body is not fully human in the animal sense. These bodies are perfectly sleek and smooth and hairless -- and this goes for men as well -- in pornographic magazines and movies. This relates to a problem we have with sexuality as animalistic. Important triggers for disgust are things that remind us we are animals and, as other animals, we will die. So we have transformed the human body, and people who enact sex [have] bodies that are not really human in the base, animal way. They are hairless and flawless and often surgically distorted. Even though we’re seeing more, we’re seeing an unreal version.

You also explore disgust in terms of gruesome images of violence and disease. In her book, A Cruel Radiance: Photography and Political Violence, Prof. Susie Linfield calls for publication of photographs of political violence and atrocity to promote human rights.

Shocking people with real life atrocities in well-crafted photographs can do that, but I think more the opposite. We are so inundated with gruesomeness at so many levels in fantasy and reality that we are inured to it and don’t react to it, which is a terrible thing. The right photograph can create the right response, but I don’t know that seeing too many of them is such a good idea. When we see pictures of starvation in the Sudan, for example, that photograph of a dying child crawling across the desert made a huge impact on me that was absolutely heart wrenching and chilling, but if I keep seeing picture after picture of death and destruction, I feel it doesn’t have much impact.

The problem is the fine line between inundation and reaction. With disgust, the more you’re exposed to something, the less disgusted you become by it. This is true in all of us. For instance, people who work in hospital emergency wards see all kinds of disgusting things all the time, and nurses or nurses’ aides deal with all kinds of body fluids. Maybe when they initially started their jobs, they had a hard time with it, but then it gets easier. This happens to everybody.

With medical professionals and first responders, is there a physiological or psychological mechanism that suppresses the disgust response?

It’s truly the idea of regression towards the mean. The more you’re exposed to something, the more boring it becomes, and the less you react to it. You become desensitized with overexposure.

I also think that the degree to which you emotionally detach from what you’re doing or what’s going on, can be a help. People who work in the medical profession are trained to emotionally detach from their patients because, if they were empathic to the degree a normal person might be, they would never be able to do their jobs. They are trained to dissociate emotionally and that, coupled with the constant exposure to gross stuff, doubles up to make it tolerable.

You use the term “benign masochism” to describe human morbid curiosity or the desire to see horror movies or stop at accident scenes.

Benign masochism is a term Paul Rozin came up with to describe the peculiar predilection of many humans to do things that would seem very unpleasant to do. Why would you subject yourself to seeing gore and horror, or why would you eat peppers [until] your mouth burns so much that you can’t taste anything, or why would you bungee jump off a building to see what that felt like? Why do we expose ourselves to these things, which are logically speaking terrifying and horrific? The explanation is that we know they are safe, and as a function of knowing they’re safe and we won’t be hurt, they serve two purposes. One is the general interest we have to dance on the edge with death. Death is such a mystery and we suppress thinking about it so much of the time that it is a release when we get to play with it in situations like horror movies or roller coaster rides and things like that.

The other side depends on our age and our personality. Your internal arousal system is a moderator for how much arousal you want from the outside. People who are set on low seek high levels of stimulation from the outside world and horror and terror give lots of arousal and help those people feel more alive. People who are set on high want to avoid those things because they’re already dealing with a lot of stimulation from the inside and so they’re trying to damp it down from outside as much as possible. Furthermore, young people generally have more desire for thrills than people over forty. So both the drive for thrills and the neurological baseline settings for how internally revved up we are work together and explain why the primary audience at horror movies are teenagers and young adults.

For writing this book, I made myself watch a couple of classic horror movies which, during the time they appeared, I had refused to see. One was The Exorcist and I was shocked by how unscary it seemed. One part of that was that in the past thirty years I have been exposed to so much more extreme, disgusting, terrifying stuff that this was nothing by comparison, and it looked fake and hokey in terms of special effects, so it didn’t have any great impact on me. I had been afraid to see it, and my expectations were not met. The same thing happened with watching Halloween. You’ve got to be kidding me.

In the horror domain now, it’s more about who can be the grossest and it has escalated. The whole point is to make it as disgusting, as gory, as blood-spattered, as evil as possible, and the content is nothing else but that. My students say it’s basically a comedy of horrors because it’s so absurd that it becomes laughable. To an extent the audience is disconnected from the mayhem because it’s so ridiculous. At the same time, there’s a competition to see who can make the grossest film as well as a drive from the audience to see the most gore possible.

The video game world has also become like movies with lots of violence and gore. The research goes both ways in terms of whether this promotes a willingness to accept violence and maybe enact violence. Regardless, to me it is a bad sign about humanity that this is taken so easily.

How is “moral disgust” related to physical disgust?

It’s both related and unrelated, and it can become related by language. For example, from the research I’ve seen, when you talk about someone stealing or lying or cheating, the use of the word disgust in that context is actually metaphorical and the feeling you really have is anger or outrage or shock. You don’t feel sick to your stomach because a student was cheating on an exam.

But by using the word disgust in a cheating situation, you can actually elicit a conditioned response within yourself that is capable of triggering a physical pang where your stomach does turn. Words can elicit conditioned responses and, because our baseline for disgust is usually on the visceral level, by simply saying “that’s disgusting” about the student who cheated on the exam, we can create a pang of physical revulsion within ourselves and then we’ll think it’s truly physically disgusting. But if instead we say “that’s terrible” or “outrageous” or some other word to convey our anger or dismay, we wouldn’t feel physically disgusted—instead we’d feel angry.

It also depends on whether the moral transgression itself is embedded with a physical disgust trigger. For example, if I stole from a colleague’s desk drawer when [he or she] was away at lunch, you might say that’s morally bad or that makes you angry, but I don’t think that disgusts anyone in a truly visceral sense. But if I said that I held my colleague up at knifepoint and threatened to stab him if he didn’t give me his money, that could evoke feelings of disgust because we’re dealing with the physical: body violation, blood, piercing the body envelope. Depending on how much viscerality is brought into the equation this will influence the degree to which disgust is felt. In fact, I’m going to run an experiment soon to test just this.

You mention that disgust taps into our fear of death.

I believe that the basic kernel of disgust is in our terror of death and our desire that it won’t happen to us. It works at multiple levels. One is to protect ourselves so we won’t ingest poisons or come into contact with diseased things that could lead to our demise. But, anything that reminds us that we are going to die triggers our repulsion.

For example, when you think about sexuality and the raw, rutting beast with two backs, that reminds us of our animality and consequently our mortality and that can disgust us. But even at a higher philosophical level, when we’re reminded that the world can be chaotic and that the universe is random and out of our control, this shatters the veneer of order and stability that we delude ourselves with and reminds us that our death is inevitable.

We’re the only creatures who have an awareness that we will die. This is a horrifying concept and we do all kinds of things to pretend that it won’t happen. But when the truth rears its ugly head, we do whatever we can to reject it, turn away from it, and the things that elicit these terrifying thoughts are disgusting to us.

I also believe that we are the only creatures who experience emotional disgust because we’re the only animals who have sophisticated and complicated enough brains to figure out the connection between say touching a man with oozing red sores who then dies a week later, and the fact that I am now covered in red sores and what that means is in store for me. To make that connection takes a lot of complexity. Unlike fear when a fire is blazing and, like other animals, we automatically know to get away, it’s different with disgust -- even if we don’t realize it at the moment, we need to think in order to be disgusted.

You write that we’d be kinder people if we were less traumatized by death.

Yes, I believe that. And there are different prescriptions for it in different cultures and religions. There are Buddhist monks who will meditate over a decomposing corpse for days as a means to come to accept death, which also necessitates not being disgusted by gruesome decomposition. They become overexposed and desensitized [to death] and then accepting of it as part of the cycle of life and able to see it as something that everything goes through and therefore that everything connects. I don’t think many people would be willing to do that, but maybe, rather than pretending that death is not going to happen, if there were more openness about it, if it was treated differently by our culture and the media, it would create a different response in us.

It’s interesting that people live as if they’ll escape death and talk about death in probabilistic terms. We’re all dying of a lethal illness and it’s called life.

I heard a story about a man who was dying of Lou Gehrig’s disease which was very hopeful and inspiring. He said it was a good thing for humanity for him to have this illness because it made him realize he’s living with an expiration date, and he said everybody’s living with an expiration date and nobody appreciates that. We don’t pay attention to the moment. We don’t live to our fullest. We waste time. We waste experience. He said it was a gift for him to realize his finite time and that more people should have that realization. I think that if we thought like this man, we’d be a lot better off and better to each other.

Has your study of disgust changed your sensitivity or behavior?

I started out with a relatively high disgust sensitivity, but it seemed to decline over the course of the research I did for the book, so I’m a classic example of someone who through over-exposure became more desensitized. On the flip side, I have gotten more germ-phobic because I have a much better understanding now of the connection between death and disease. I’m much more likely to open the public restroom door with my elbow and do more of that sort of thing than before. The upside is that I’ve had fewer colds in the past couple of years.

Is there anything else you’d like to add on what you hope readers will take from your book on disgust?

I’d like readers to take away that disgust is under our control because it is so psychologically manipulable. We can choose when to be disgusted. Under certain circumstances, particularly social ones where we can be manipulated, we might want to step back and ask whether it’s worth being disgusted, or maybe if we stopped to think about it we’d discover that that we’re not disgusted and actually feeling something else. In general, more mindful living is a lesson I would hope people could learn from the realization that we can take control of disgust and to understand the origins of disgust and why we feel it in ourselves both specifically and philosophically.