What Is the Cooties Heuristic?

Mine is a tea drinking family, and I will sometimes sweeten my cuppa with an artificial sweetener. A couple years ago, I read that this sweetener was discovered by accident: A chemist was working on developing a new insecticide, and he inadvertently let some of his solution touch his lips. It tasted remarkably like sugar, so he just switched course and developed a new sugar substitute instead. Now, if my wife is making me tea, she will call from the kitchen: “Cream? Insecticide?”

Does this disgust you? Does it seem unnatural to you? If so, you are experiencing the cooties heuristic, an ancient aversion to impurities that has some surprising ways of expressing itself in the modern world. A lot of people hate the idea of putting any kind of contaminant into their body, and will go to great lengths to avoid chemicals and additives in their food. The food industry long ago noticed this aversion: Marketers have slapped the words “all natural” on everything from sugary drinks to red meat to grab the attention of purists.

But what does “natural” mean to us really? It obviously doesn’t mean that it occurs in nature. Arsenic is #33 on the periodic table, yet we all know not to add it to our elderberry wine. So when we use the word “natural,” what do we mean?

University of Pennsylvania psychologist Paul Rozin has studied this question at some length. In one revealing experiment, for example, he decided that the best way to define “naturalness” was to see what destroyed “naturalness” in people’s minds. That is, he picked things that most people would consider natural when they come out of the ground, and perverted them in various ways, to see what was acceptable and what was not.

He chose water and peanuts. You could argue this, but they’re pretty good choices. After all, everyone drinks H2O in one form or another; otherwise you die. Rozin chose mountain spring water, which has a special claim on naturalness in many people’s minds. And peanuts are not a bad food choice: They grow inside shells, so they’re somewhat protected, and they are ubiquitous in “health foods” like granola bars and organic peanut butter and so forth. For the purposes of this experiment, the peanuts were grown without fertilizers or insecticides.

So he started with a diet of spring water and peanuts. Then he changed this natural diet in many different ways, and asked people how they felt about each of the transformations: Is it still natural or is it unnatural, or somewhere in between? With water, for example, how about mixing water from two mountain springs? Is it still pure? Or freezing it, or boiling it? How about adding a trace amount (0.001%) of minerals? And so forth. He made similar changes to the peanuts, and collected people’s reactions: Would you mind mixing peanuts from Georgia and peanuts from North Carolina? Removing or adding fat? Grinding them into peanut butter? Freezing them, and then grinding them into peanut butter? And so forth.

In general, Rozin found that people didn’t mind physical transformations nearly as much as they minded chemical changes to their food and water. So for example, most say it’s okay to mix water from two springs (or peanuts from two farms). And they don’t care too much if these things have been frozen, especially if they have been frozen outdoors by Mother Nature. But they do see even trace amounts of additives as contamination: More than half objected to adding trace minerals to water, even if they were precisely the same concentration of minerals that exist in natural sea water. People similarly felt that adding mineral additives in their peanut butter destroyed its naturalness.

This is interesting, but Rozin wanted to look at a diet that more closely resembles what people actually eat day to day—or what they might eat in the future. So he gave people a long list of foods that had been processed or altered a wide variety of ways, to see what people viewed as unnatural. Here’s just a partial list of the many foods they chose from: “fresh squeezed” orange juice; OJ with a calcium supplement; milk fresh from a cow; milk fresh from a zebra; pasteurized milk; skim milk; a steak from a free-range cow; wild strawberries; commercially grown strawberries; a wolf; a German shepherd; an elephant; an oak tree; a penguin; corn with a gene from a cow to make it insect-resistant; a pig with a corn gene to make it grow faster; a pig with a penguin gene to make it more tolerant of cold.

You get the idea. Most of us eat some of these foods every day, even some of the “transformed” foods. But some of us are more adventurous than others and everyone has his own personal taboos. Is “wild” preferable to “domesticated”? I may be perfectly okay with something that you find repulsive, and vice versa. When Rozin analyzed the data from this study, he discovered a few patterns in people’s preferences and prohibitions. Most notably, people object to processing much more than they care about the actual content. So for example, fresh zebra milk is much less objectionable than cow’s milk that has had fat removed or added to make skim milk or cream. People will stretch their boundaries about unusual food choices as long as the food isn’t tampered with too much.

The bottom line is that we simply don’t like fooling with Mother Nature. Perhaps unsurprisingly, people reserve their harshest judgments for genetically modified foods, and again it was the idea itself that people found objectionable—rather than the particulars. Whether it was moving a plant gene to an animal or an animal gene to plant or even plant to plant, it didn’t matter: We see this kind of manipulation as undermining the natural state of what we put in our bodies.

All of this points to a contagion heuristic, an automatic neuronal bias for things in a pure and natural state—and against impurities and unnatural essences. It’s a simple rule: Avoid contaminants. Other Rozin findings support this idea: He found, for example, that people don’t much care how much of a foreign ingredient is added to their food. Even a trace amount renders it unnatural and therefore unappealing. And it appears to be additions, more than subtractions, that ruin food; removing an impurity from an otherwise natural food does not make it “more natural.” This cognitive bias against adding would help explain another popular marketing phrase: “no additives.”

This contagion bias almost certainly originated in pre-historical times—long before our ancestors understood modern germ theory. It was (and remains) deeply entangled with feelings of disgust, which helped early humans avoid infection and food poisoning and so forth. But the heuristic remains deep-wired in our brains, and as with a lot of heuristics, its modern-day expression is not always rational. But here’s the thing: We know in our modern minds that the beliefs are irrational. How else do you explain the “5-second rule”? This widely accepted cultural “rule” says that if you drop some food on the floor, it’s still okay to eat if you pick it up within five seconds. Some say three seconds, other ten, but the rule is ubiquitous; the Russians simply say: “Quickly picked up is not fallen.”It’s widely popular because, medically, it is okay. It may gross out some people’s ancient sensibilities, but you’re almost certainly not going to come down with a disease from brushing off a pretzel.

When Rozin and his colleagues asked people to explain their preferences for things that are natural, they got an intriguing answer. Two answers really: Many say they prefer naturalness because it is healthier and kinder to the environment. That’s the modern mind talking: These are sensible answers, based on evidence—or at least what we think is true. But just as many people say they prefer natural things because they are inherently “better”—more moral, more aesthetic. Natural things are simply “right.” This is the ancient heuristic talking. The bias is so deeply ingrained that it doesn’t require rational explanation.

One could argue that these ancient contagion beliefs are still adaptive—that what feels “right” is also in most cases healthier. And indeed, many vegans describe their life choice as both a moral and a healthy choice. But what about when these deep-rooted impulses emerge in other realms of life, having nothing to do with food or nutrition?

Many of the contagion beliefs that linger in the modern mind are a form of magical thinking. Think of cooties. Cooties are fictional germs that spread on contact; they are disgusting and they are everywhere, and nowhere more prevalent than in the vivid imagination of just about every American child. They are often carried by unpopular kids, and almost always by kids of the opposite sex, and they clearly have a moral dimension: Indeed, one is much more likely to “catch” a classmate’s unpopularity from cooties than to come down with a fever.

Cooties are part of the harmless magical thinking of childhood. But the adult versions of cooties are often not as benign. Just think about sweaters.

There is a whole line of contagion research involving adult sweaters. Imaginary sweaters, all thoroughly laundered. What psychologists do is ask people which sweaters they would be willing to wear, or not. For example, would you wear a sweater once worn by Adolph Hitler? A lot of people would not, and psychologists take this as evidence for the potency of the contagion heuristic. Merely touching something once touched by evil “essences” can potentially infect one with those essences.

There is no actual Hitler’s sweater. It’s hard to even imagine him in a pullover. It’s a laboratory paradigm. Researchers have used the sweater paradigm to study various kinds of contagion, and more importantly to explore the nature of the essences that people tend to avoid. For example, one team of psychologists used such fictional sweaters to study attitudes towards people with AIDS. It’s long been known (and many surveys have shown) that people’s aversion to AIDS victims is both moral and medical. And anecdotal evidence suggests that this prejudice is rooted in misguided contagion beliefs. People are reluctant to buy houses owned by AIDS victims; to work in the same workplace, and to have their child go to school with a classmate who has AIDS.

These attitudes were documented long after HIV transmission was well understood, so they are clearly irrational, uninformed by science. Psychologists have since shown the heuristic roots of such magical thinking. They asked people, how likely would you be to wear a sweater worn by someone with AIDS? A gay man with AIDS? A man who got AIDS from a transfusion? For comparison, they also asked about other hypothetical sweater owners. Would you wear a sweater worn by a man who had tuberculosis? A man who has lost his limb in an automobile accident? And so forth. In every case, the researchers make it absolutely clear that the sweater has been thoroughly washed, to make sure that their aversion is not an actual fear of real germs. The idea was to sort out the components of contagion beliefs: How much of the aversion is based on irrational fear of disease? How much on moral disapproval? How much on aversion to any misfortune? The findings were interesting and disturbing. People didn’t stigmatize TB; they just didn’t want to catch it. But all of these biases—against disease, immorality and misfortune—appear to be active in the stigmatization of AIDS victims, which makes it particularly difficult to overcome.

Psychologists have also studied the sweaters of good and admirable people, like Mother Teresa. And they do find that people believe they can pick up the good essences as well. That may explain in part why people wear and cherish their grandmother’s wedding ring. But in general the good essences are not as powerful as bad essences. That is, Mother Teresa can’t undo the evil contagion of Hitler’s sweater simply by wearing it later on.

There may be one exception to this rule, however, and that is land. Consider the enduring land disputes in Israel and the Gaza Strip. Such disputes are as ancient as mankind, but the notion of national land is relatively new in human history. In prehistoric days, emotional attachments to “place” were more personal and sacred than abstract and legalistic, as it is today. Why is that? What is it about a particular plot of land that stirs such deep passions in us? Rozin, working with his University of Pennsylvania colleague Sharon Wolf, decided to explore the role of contagion beliefs in the ongoing land disputes of the Middle East, specifically the land of Israel. They figured that land, at least as much as sweaters, could be perceived as having either good or bad essences. Indeed, ancestral Jewish land could be imbued with associations so powerful that they would make trading or forfeiting the land taboo—even for a similar plot of land elsewhere. Enemy-occupied land would similarly be imbued with negative essences, thus creating a fundamental psychological conflict over the land of Israel. How, they wondered, does this primeval cognitive battle play out in the modern Jewish mind?

As part of this research, the psychologists devised a laboratory tool to measure peoples’ propensity for positive and negative contagion beliefs, and they used it to study Israelis and American Jews. They asked them specific questions about their attachment to the land of Israel: Would they trade any part of East Jerusalem? The Temple Mount? An unoccupied parcel of Israeli land? And if so, to whom? Syria? Jordan?

In general, both Israelis and American Jews considered the land of Israel “untradeable.” This was true not only for sacred sites like East Jerusalem, but also for unnamed parcels of border property. When asked about Har Herzl, a Jerusalem burial ground for the Zionist leader Teodor Herzl and assassinated Prime Minister Itzak Rabin, fully 83 percent of Israelis and 70 percent of American Jews said they “would never trade it for land, or anything else.” The majority of respondents put the land of Israel in a category with one’s children or one’s religion—completely off the table.

But Rozin and Wolf (who did this study before the 2009 Gaza dispute) wanted to sort out the psychology underlying such strong land attachments. So they asked some hypothetical questions about Har Herzl. First, they told the volunteers to imagine that an earthquake hit Jerusalem, destroying the cemetery and wiping out 50 feet of soil in the process; all of the bodies have been moved to a different burial site. Would you now trade Har Herzl? Then they added another wrinkle: Imagine that, after the earthquake, a prison was built on the site of Har Herzl, specifically for Palestinian political prisoners. The prison has existed for a decade. Would you now trade the land?

The idea was to see what it is about the land that Jews are really attached to emotionally—and what it would take to sever those attachments. And it appears it’s the soil itself that contains the positive ancestral essences. Following the hypothetical earthquake, significantly fewer were rigidly opposed to trading the land (39 percent of Israelis, compared to 85 percent before the earthquake). Even fewer were opposed to trading after the land had been “contaminated” by the enemy presence in the imaginary prison.

Yet a significant number of participants held steadfastly to their no-trade views even following the presence of a perceived enemy for 10 years. Land that has long been occupied by an “enemy”—not only in Gaza, but various Mideast regions—should be infused with negative associations and Jews should not be attached to it. Indeed, if the Hitler-Mother Teresa finding holds true, the negative associations should overpower the positive ones. Yet many Jews remain attached to enemy-occupied land, just as many Arabs have strong emotional ties to parts of Israel. One possible explanation, the psychologists say, is that original positive associations establish priority, trumping negative essences that come later.

There are of course a lot of other issues at work in the conflicts of Israel and the region, but the scientists went to great pains to control scientifically for many of them—feelings of vulnerability, political views about Israel, and so forth. These other factors didn’t diminish the positive, primal attachment to the land itself. It seems the ancient contagion heuristic stakes a psychological claim that is hard to shake.

I don’t consider myself a superstitious person, generally speaking. I open umbrellas in the house and walk under ladders—and I think it’s silly that hotels often don’t have a 13th floor. But I would be hard-pressed to wear Hitler’s sweater, for the same reason I am finicky about cleanliness. I came by my aversions naturally, because nature is often perilous—a lesson our ancestors probably learned the hard way.

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