Hood, Bruce - Supersense

Some things automatically trigger disgust and don’t have to be learned. Hydrogen sulphide, methane, cadaverine, and putrescine are four of the most revolting smells to the human nose. They can be found in various bodily excretions but are most concentrated in a decomposing corpse. When I trod on the stomach of that dead cat as a ten-year-old, it was this chemical cocktail that assaulted my senses. Everyone feels disgusted by the smell of putrefying bodies. However, other triggers of disgust are not so hardwired into our biology, and that is why disgust is so interesting to psychologists: sometimes it can be triggered by belief alone.

When we met Paul Rozin earlier, it was in the context of the killer’s cardigan, but this research stems from his work on the origins and development of human disgust. Rozin is one of the most disgusting researchers in the world. After reading about his studies, you would be very wary about stopping over for dinner at his place. 44For example, he measures how adults respond to various challenges that trigger the ‘yuck’ response. Could you drink out of a glass after it has been touched with a sterilized cockroach? Could you eat a delicious piece of chocolate fudge shaped like a dog turd? Would you slurp your favourite soup after it had been stirred with a brand-new fly swatter? Why does spitting on your own food make it disgusting despite the fact that you need saliva for digestion? As you would expect, people are disgusted at the prospect of most of these challenges, even though the actual risk of contamination is minimal or nonexistent in each situation.

And then there are cultural variations. Many of us could quite happily tuck into a bacon sandwich (apparently one of the most difficult things for former meat-eaters to give up when they become vegetarian), whereas a devout Arab or Jew would consider it disgusting. In the West, we are appalled at the ease with which insects, penises, gall bladders, snakes, cats, dogs, and monkeys are consumed in the Far East. Clearly some forms of disgust are culturally determined. How can this be?

ESSENTIAL CONTAMINATION

Cultural variations prove that some triggers for disgust must be learned. When we watch others turning up their noses at particular foods or retching at certain sights, we can copy their responses. But disgust and the accompanying fear of contamination do not follow simple learning rules in the normal way. For a start, we are wired to respond automatically to others’ disgust. Simply watching someone pull a disgusted expression is sufficient to induce our own feelings of disgust. For example, if you watch somebody pull a face after sniffing a drink, this activates the insula, the same region of your brain that normally fires when you yourself smell something offensive. 45It’s one-trial learning. That’s how rapid and infectious disgust emotions can be.

For me, the really interesting aspect of disgust and the associated contamination fears is that they show all the hallmarks of supernatural thinking. 46This is because they trigger psychological essentialism, vitalistic reasoning, and sympathetic magic. For example, sympathetic magic states that an essence can be transferred on contact and that it continues to exert an influence after that contact has ceased. This is known as the ‘once in contact, always in contact’ principle. 47Something you cherish can be ruined by coming into contact with a disgusting contaminant in exactly the same way. For example, the briefest touch of your food by someone you think is disgusting makes the dish unpalatable. There’s an old saying that a drop of oil can spoil a barrel of honey, but a drop of honey can’t ruin a barrel of oil. This is the negative bias that humans hold when it comes to contamination. 48We intuitively feel that the integrity of something good can be more easily spoiled by contact with something bad rather than the other way around.

However, it’s difficult to be reasonable about contamination once it’s occurred. It’s as if the contaminant has energy that can spread. For example, imagine that your favourite dessert is cherry pie and that you have the option of choosing between a very large slice and a much smaller piece. Unfortunately, your waiter accidentally touches the crust of the large slice with his dirty thumb. The same thumb that you just saw him pick his nose with. Which slice would you choose? Given the choice, most of us would opt for the smaller slice, even though we could cut off the crust where the waiter touched it and still end up with more pie. As far as we are concerned, the whole slice has been ruined – as well as our appetite.

THE WISDOM OF REPUGNANCE

Disgust affects more than just our attitudes toward the things we put in our mouths. It clouds our moral judgements too. Many people rely on disgust in deciding what they think is right or wrong. Leon Kass, the former chief ethical adviser to President George W. Bush, argued that disgust is a reliable barometer to what we should find morally unacceptable, the so-called knee-jerk response. In his essay ‘The Wisdom of Repugnance’, he makes the case that disgust reflects deep-seated notions and should be interpreted as evidence for the intrinsically harmful or evil nature of something. 49If you feel disgusted when you hear about some event, then that’s because it is wrong. The problem with this view is that what people find disgusting depends on whom you ask.

Consider incest between a consenting brother and sister. In most societies, brother and sister incest is regarded as disgusting. Why? What is wrong with two genetically related people having sex? We could argue that this response evolved because of the risks of inbreeding. For example, mating with your sibling is a genetic no-no, as there is an increased chance that any offspring would have genetic abnormalities. And yet if a brother and sister have consensual sexual intercourse in private so that no one would ever know, using birth control and basically avoiding any possible chance of pregnancy, we still consider such sex morally unacceptable. Then there are all the other weird things that people might get up to. Why is cleaning the toilet with the national flag or eating a chicken carcass you have just used for masturbation disgusting? These acts might be weird, but there is no intrinsic reason for why they are wrong. 50What’s wrong with wearing a killer’s cardigan? In fact, people are often lost for words when trying to give reasons. They are morally dumb-founded, as the psychologist Jonathan Haidt says. 51By the way, just in case you wondered about the warped state of my own mind, these disturbing examples all come from Haidt’s work. So write to him if they upset you.

Biological explanations are too limited for explaining all the things we find disgusting. Rather, the answer must be some other mechanism that uses disgust responses for some other purpose. One possibility is that disgust works as a mechanism for social cohesion. To form a cohesive group we must have sets of rules, beliefs, and practices that define our group and that each member must agree to abide by. This is how one gang distinguishes itself from another. These are the moral codes of conduct found throughout the different cultures of the world. When these rules are violated, a taboo has been broken, and a negative emotional response must be triggered. The perpetrator must feel guilt, and the rest of us must punish that person. This is how justice works. The net effect is to strengthen the cohesion of the group.

Culturally defined taboos may engender social cohesion, but they are not based on any reason other than that they define the group. This is why those individuals who are happy to touch a killer’s cardigan are outsiders. By taking a behaviour and linking it to a visceral response, we can use disgust to control individual group members. We can also use disgust to ostracize others. In the next chapter, we examine how such essential thinking is at the root of bigotry directed towards people who some would rather keep at arm’s length because of their colour or social background. When we say the peasants are revolting, we mean it in a disgusted way. It provides the emotional reason for treating them the way oppressors do. We can treat others badly who do not share our values because it feels right. And why does it feel right? I think the answer is that a supersense of invisible properties operating in the world makes these feelings seem reasonable, and disgust is the negative consequence of violating our sacred values.