positively inedible to his friends. If you want to figure out what makes something unpleasant, chili peppers are an interesting test case.
Rozin says that there’s no question that eating chili peppers is an innately negative experience. “We have all kinds of evidence that little children don’t like this taste.” In some chili-eating cultures, women rub chili powder on their breasts to speed up the weaning process.
There’s a lot of conjecture about why people started to eat chilies in the first place, because evidence has shown that they’ve been part of the human diet for approximately nine thousand years. Some ethnopharmacologists (yes, there is such a discipline—the field even has its own journal) have suggested that the Maya ate peppers for their antimicrobial properties.{8} More recently, scientists in Canada have shown that despite their potential for setting the lining of your esophagus and stomach on fire, chilies contain a chemical that suppresses the gut bacteria
Are people eating chili peppers for their health, then? “I’m not convinced of it,” says Rozin. The evidence is circumstantial at best. Presumably, ancient cultures were unaware that the Nobel Prize would be awarded in 2005 for the discovery of the relationship between
There are other theories about pepper’s popularity. “There’s the idea that it disguises decay,” says Rozin. “People were eating food without refrigerators, and they put this thing on, and they wouldn’t notice decay. I don’t think that makes a lot of sense.”
It’s also true that chili peppers contain large amounts of vitamins A and C. “Surely, there are better ways to get your vitamins without having to burn your mouth off,” says Rozin.
To learn what was really behind people’s passion for peppers, in the late 1970s Rozin and some colleagues visited a village in the Mexican highlands near Oaxaca. Except for the smallest children, nearly everyone in the village ate peppers in one form or another every day, and it clearly was not a case of “Eat your chili or you won’t get dessert.” To prove this, he conducted a simple experiment.
The local markets sold treats in cellophane packets. The treats came in two varieties: sweet and savory. The sweet kind consisted of sour fruits flavored with sugar. The savory type was ground chili peppers mixed with salt. Rozin bought up the town’s supply of these packets—not a major investment, because they were only a penny apiece—and gave children a choice: sweet or savory. Children who were older than five routinely picked the chili- and-salt treat over the sugar-and-fruit one.
Rozin also discovered that people actually like the burning feeling in their mouths that lingers even after the pepper is swallowed. This pleasure appears to be limited to the mouth. No one seems to like the burn of a chili pepper in the eye.
Animals apparently do not experience a similar pleasure from pain. To prove this, Rozin’s team offered the pigs and the dogs in the village a choice of a tortilla with hot sauce and a tortilla without. “We did not find a single animal in the village who would take the hot one first,” he says.
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
