Many researchers have suggested that the reason people tolerate the chili burn is that they become inured to it, although this doesn’t answer the question of why people start to eat chilies in the first place. This is known as the desensitization theory. The chemical that packs the chili’s punch is called capsaicin. “It’s been known for many years that you can desensitize nerve fibers to capsaicin,” says David Julius. In 1997, Julius identified the receptor that responds to capsaicin.
Julius says that with repeated exposure, capsaicin can actually cause damage to the nerve fibers. The damage is reversible, though: the nerve fiber can recover with time. For a certain period of time, however, the nerve is less able to signal to the brain.
Rozin doesn’t think that desensitization explains people’s chili-eating behavior, either. Yes, he says, there probably is some desensitization taking place, but “there would have to be positive features of chili that support a preference after desensitization; otherwise, desensitization would lead to neutral responses.”{10} In other words, desensitization explains only why people can tolerate chilies, not why they actually like to eat them.
There are four lines of experimental evidence to support Rozin’s position. In his studies, Rozin has measured the threshold at which people can detect a chili’s burning sensation. If the desensitization hypothesis were correct, then people who eat a lot of chilies should have a higher threshold for detecting the burn. So Rozin tested the residents of the Mexican village, who eat a lot of chilies, and compared their thresholds with students at the University of Pennsylvania, who ate far fewer chilies. There was only a tiny difference.
The second line of evidence is that Penn students who like chili peppers should have a higher threshold than students who don’t. Again, the difference was marginal.
Third, people who really like chilies should have a higher threshold for detecting the burning sensation, but Rozin showed that there was no relationship between taste preference and threshold.
Finally, if you eat chilies every day of your life, your threshold should get higher with age—but it doesn’t.
Rozin believes that the solution to the chili mystery is what he calls hedonic reversal. Something that tastes terrible when you first eat it over time becomes a delightful taste. “It’s something in your brain that’s switched from a negative evaluation to a positive evaluation,” he says.
This does not happen only with chilies. Rozin attributes it to a more general phenomenon known as benign masochism. We like to do things that are innately negative. For example, says Rozin, people like to go to sad movies, even though they make us cry. People like disgusting jokes, even though these are, well, disgusting. Some people even like pain. For certain people, pain and pleasure have a long history of coexisting.
“What kind of crazy species are we?” asks Rozin. For example, people actually line up and pay money to have the wits scared out of them on a roller coaster. “Can you imagine a dog going on a roller coaster and paying for a second ride? We are the only species, as far as I know, to seek out innately negative events.”
Although Rozin is certain that the phenomenon of hedonic reversal is real, he’s less certain about why it happens. He does have a theory. “People get pleasure out of the fact that their bodies are telling them something that they know is not the case,” he says. So, on a roller coaster you can be excited, even titillated by the fear, because you know you’re not really threatened. “In a sad movie, you’re crying and enjoying it because it’s not really sad. Your body is being tricked into feeling it’s sad, but you know it’s not really happening. That sort of disparity becomes a source of pleasure, but only for humans.”
If you’re a fan of chili peppers, you might be thinking it’s simpler than this: they taste good. In fact, you may have a brand preference when it comes to hot sauce or a favorite variety of spicy peppers, which would seem to point to flavor as a key factor. The innately negative part, the burning of your tongue, may not have much of an attraction for you at all.
Michael Cunningham, a professor of psychology and communication at the University of Louisville in Kentucky, agrees with you. “Hedonic reversals are tricky,” he says. “I think there is a combination of positive emotion mixed in with the negative.”
Take roller coasters. “With roller coasters, you get the vistas,” he says. “You get the sensation of speed. I don’t know whether the predominant reaction is one of fear. I think it’s exhilaration, with a little bit of fear thrown in.” Besides, for some people there’s a kind of joy that accompanies an adrenaline rush.
Cunningham also sees a positive side to sadness. “Sadness is nature’s way of putting things in perspective,” he says. “You slow down your rate of thinking, and you do some reevaluating, so it can have a positive aspect to it.”
As for chili peppers, Cunningham says that even with scalding-hot chili peppers, it’s not simply about pain. A pleasurable taste exists in there somewhere; otherwise, people wouldn’t be eating them. “People don’t just drip sulfuric acid on their tongues,” he says. “At least, I’m not aware of any people who do.”
It’s possible that the principle behind hedonic reversal is a variation of the phenomenon known as “runner’s high.” Certain chemicals produced by the brain act the way that morphine and other opioid painkillers do. Studies show that the body produces these chemicals in greater numbers after a long run, but they may also be created in response to painful or even strongly emotional experiences. Perhaps hedonic reversal is a shortcut to running a marathon. Or maybe it’s related to that joke about the man who is seen banging his head against a wall. When asked why he is doing this, he replies, “Because it feels so good when I stop.”
Hedonic reversal does not apply universally. “Nausea is one of the few negative sensations that I think nobody enjoys,” says Rozin, although he’s not exactly sure why. One possibility is that nausea is inevitably caused by, or followed by, something truly bad. “It’s very difficult to be nauseous and not have something wrong,” says Rozin. “You can feel pain, as in a massage, and not really have anything wrong with your body. Nausea is a pretty reliable symptom of something going wrong.”
Yale psychologist Paul Bloom agrees with Rozin that part of the pleasure of painful stimuli is that as long as it is safe—that is, as long as a movie or a chili pepper doesn’t actually endanger us—then we can enjoy it. Yet horror movies and hot peppers evoke strong sensations, just as love stories do. Perhaps the reversal works only if there is some distance between our normal, resting state and the intensity of the emotion. Maybe this is why annoyances are not really susceptible to hedonic reversal. By their nature, annoyances are minor. What fun is it to experience a minor annoyance? It would be akin to the fun of eating bland food. In fact, there’s a famous Mel Brooks quote along these lines: “I cut my finger. That’s tragedy. A man walks into an open sewer and dies. That’s comedy.”
If annoyances are mild, though, how is mildness measured? How much is too much? For any field of scientific endeavor, taking measurements is key. How hard is a particular mineral? At what temperature does a compound freeze? How much carbon dioxide is being released into the atmosphere? What is the red shift of a particular quasar? How long does it take a rat to complete a maze? Accurate measurements are essential to the progress of science.
One of the biggest challenges facing a new scientific field, such as the study of annoyance, is that it has to develop the instruments to take measurements. There are no annoyingometers (although most people do come equipped with annoydar) and no well-validated personality inventories. Clearly, if progress is to be made in understanding why certain things or people are so irritating, scientists will need ways to answer two kinds of questions: how annoying someone or something is, and how much someone is annoyed by things or people in his or her environment.