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Tyler Cowen, perhaps our most food-aware economist, noted that he is often puzzled to hear, as that day's lunch choice is being deliberated, someone utter something like “I don't want Thai food today; I just had that yesterday.” This rather neglects the fact that Thais are eating Thai food
every day
. “
Would it be so terrible,” he wondered, “to eat only Indian food, whether at home or in restaurants, every day for a week?” Often, when we think we are tired of something, we may simply be forgetting how much variety we have actually had (in a phenomenon that has been called “
variety amnesia”). Curiously, while one might expect people to tire less quickly of flavorful food, food monotony research at Natick has shown the opposite: The more bland it is, the less quickly soldiers grew tired of it. Bland food, after all, fades from memory more quickly than exciting food. The less you remember having it, the less tired of it you get.

Natick also had to grapple with
where
food was being consumed. The very same food will be rated higher when served in a restaurant versus an institutional cafeteria or a lab. Soldiers in the field face two challenges: Not only are they eating MREs, with their limited variety and entrées of approximate flavor and dubious texture, but they are often eating them in the far-flung, inhospitable environments for which they were designed. In a series of groundbreaking experiments, a group of soldiers (bivouacked on an island in Hawaii) and MIT students (on campus) ate nothing but MREs. The soldiers ate them for thirty-four days straight, the students for forty-five days. Both groups deemed the food “acceptable” (which did not speak well for MIT's canteen). Both groups lost weight. The students, however, ate more than the soldiers in the field. The experiments showed the importance of
context
on liking. For many reasons, it is more difficult to get people in the field to eat.

Context is no less important in the real world.
People eating in an ethnic restaurant with appropriate decor rate the food higher; add some red-checkered tablecloths or a Sergio Leone poster, they eat more pasta. The loudness, and type, of music can affect the way we feel about our food. We eat more when we are in larger groups. The type of glassware, the weight of plates, whether the color of the food matches the color of the plate—even how long people have to wait for their meal—all have been shown to influence how much we like, and eat, food.

There is a poignant scene in the film
Sideways
in which Miles, the hapless protagonist, in a fit of pique and despair over his dismal life prospects, brings his treasured bottle of 1961 Cheval Blanc to a fast-food joint. Amid the harsh light and the smell of grease, to the accompaniment of a burger and onion rings, he surreptitiously quaffs his “special occasion wine” from a Styrofoam cup. The wine is still the same wine, and if consumption were always just about the thing being consumed, the level of enjoyment should theoretically be the same. But all the context factors are “off”: He is alone, he is eating mediocre food, he does not have a proper glass, the decor is terrible. He is drinking with vengeance, not appreciation.

Context is not just place but time. Your love of breakfast cereals probably does not, in normal circumstances, extend to dinner. Breakfast itself is a rather strange meal, as the Dutch researcher E. P. Köster has observed.
The most adventurous gourmands will eat the same thing for
breakfast, day after day. They would hardly contemplate this at dinner. Sheer convenience explains much of it, to be sure, but research suggests there are whole classes of textures that are less liked at breakfast, varying by culture. By the time our after-dinner dessert rolls around, we are hungry for variety. It is as if we wake up less primed to desire novelty, our threshold for excitement slowly ramping up as the day progresses.

Back at the Warfighter Café, I contemplated the spread before me. How did the MREs of tomorrow stand up? Did they still deserve the unfortunate sobriquets such as “meals refusing to exit” or “meals rejected by Ethiopians”? I took a bite of “MATS Salmon,” “MATS” standing for “microwave-assisted thermal sterilization.” The name could use a little work and the fish was, admittedly, a bit tough. “It's a little chewier than we'd like,” Darsch told me. Not surprisingly: The salmon had been bombarded with over 120,000 psi of pressure, literally rupturing the cell walls of any lingering bacteria with the ruthlessness of a bunker-busting bomb. But the taste was there, at least more than one would expect for a shrink-wrapped piece of room-temperature fish with no immediate sell-by date. Would it fly at Del Posto? No. But to a soldier faced with a long-range patrol in a hot desert, it might be just good enough.

On the morning I went to Philadelphia to meet Marcia Pelchat, a longtime researcher at Monell, I was nursing a slight cold. When I arrived at her office, Pelchat, a petite, polite woman with a disarming sense of humor, offered me coffee. I asked if she had tea, explaining that whenever I have a cold, I prefer tea, which suddenly seems to taste better than coffee. She considered it for a moment, then said, “Coffee without the aroma would seem like ashes to me.”

Here is that thing that is so easy to forget yet never fails to startle when we experience it firsthand: Most of the action when we are tasting something comes from the nose. Coffee is one of those curious things that smells better than it tastes, and to lose the smell of it is in essence to lose what we like about it. To remind yourself of this basic sensory
fact, it is worth, every once in a while, administering to yourself what Pelchat does to me on this morning: the jelly-bean test. She handed me three jelly beans and asked me to hold my already stuffed nose. They each tasted, simply, sweet. When I released my nostrils on the last jelly bean, I suddenly experienced, even with my cold, a spreading flood of flavor, something like Häagen-Dazs coffee ice cream, through the back of my mouth and nose. I had, in fact, just eaten a coffee-flavored jelly bean, as well as its banana- and licorice-flavored cousins.

Our taste-bud-studded tongues do the basic sensory sorting: sweet, sour, bitter, salty, and, less officially, umami (and maybe fat). But all the finer distinctions—mango versus papaya, lamb versus pork—come “retronasally,” from the mouth up through the nasal passage, as a smell. The things we know as strawberries or Coca-Cola or
sriracha
sauce are not tastes; they are flavors. There is, strictly speaking, no “taste of honey”; there is “retronasal olfaction of honey.” Honey, to be honey, needs to waft on a gust of inhaled air into our nasopharynx. Even seemingly strong “tastes,” like lemon, only read on the tongue as a collection of sours and bitters and sweets.
Terpenes triggering receptors in the olfactory mucosa make lemon lemony.

How we perceive something, Paul Rozin has argued, influences how we feel about it. Even people who do not like the taste of coffee can no doubt appreciate the aroma. By contrast, on a plate, Limburger cheese may strike us, via our nose, as unpleasant. Once in the mouth, however, it undergoes a stunning change into something we may find pleasurable. It is as if the brain, sensing that food is in the mouth, and thus no longer represents some external hazard, shifts its whole outlook. Give someone who has a nose-blocking cold a cup of beef broth to which yellow food coloring has been added, Pelchat told me, and he will think he is eating chicken soup. Take away the retronasal passage, and it would be like going from a cable television package with an almost infinite number of channels down to a handful of networks playing the same old shows.

But I have come to Pelchat's office to talk about liking. Regardless of which part of my mouth and nasal cavities are telling me what the flavor is, what is telling me I like it? Virginia Woolf once wrote that “
reading is a longer and more complicated process than seeing.” So too is the question of whether we like something more than feeling a sensory response to something we have put in our mouths.
What we
like is sometimes corrupted by what we know we like. A study that had consumers test pineapple varieties found those who preferred pineapples labeled “organic” and “free trade” tended to be those who were more fond of organic and free trade produce itself. Those less keen on organics were less happy about the pineapple. As the researchers noted, “
The same cognitive information evoked opposite affective reactions in different subjects.”

Pelchat, it turned out, did have some tea for me. But first she wanted me to take a capsule, which would contain either sugar or, simply, non-caloric cellulose. She wanted to show me the taste mechanism known as “flavor-nutrient” conditioning—the idea that we like what makes us feel good,
even if we do not know it
.

The power of this conditioning has been shown in any number of studies on rats, our fellow neophobic omnivores. Typically, a rat will drink, ad libitum (as much as it wants), something like orange Kool-Aid. Rats, as a cursory glance at the scientific literature reveals, drink a
lot
of Kool-Aid. Meanwhile, sometime before, during, or after, a sweetener will be “infused,” via “intragastric catheter,” directly to its stomach. Later, the rat will sample grape Kool-Aid without getting the sugar drip to the stomach. When both flavors are later tested, rats will prefer the one that
was
sweetened, even when both flavors are now unsweetened. Sometimes they still cling to the old favorite when one of the
new
options actually tastes sweet in the moment.

Curiously, the way the rat came to like one flavor over another had nothing to do with a taste preference. How do researchers know? “In fact,” Pelchat tells me, her voice lowering a bit, “the esophagus is externalized.” With the gullet sitting outside its body, the rat cannot taste the glucose, nor could he belch it back up into his mouth. Infused into the stomach, however, that sweetness still provides a hedonic payoff. “Something in the gut or the metabolic system is making them like that flavor,” Pelchat said.

Pelchat wondered if humans' sensory mechanisms could be similarly bypassed, without such extreme surgery. So she once swallowed a nasogastric tube for a day and tried to mainline glucose. “I thought, I know what I'm doing, I'll pretend it's food and I'll swallow it, it'll be fine. Instead, I was puking, tearing up.” Finally, she hit upon pills, which would or would not release sweetness into the gut. A placebo cellulose pill has no calories, no benefit for the body. Well, almost no
benefit. “Incidentally,” she noted with a laugh as I inspected a pill, “that will keep you regular.”
In her study, people who downed the (tasteless) sugar pills ended up liking the flavor of tea more than the tea they drank with the unsweetened pills.

So without even knowing why, people preferred one tea over another (
we are strangers to our taste
). They were getting “post-ingestive” signals, in the form of a nutritional reward, that predisposed them toward a flavor. “I always make a point of telling people that reward and pleasure are not the same thing,” she says. “Food can be rewarding without the conscious experience of pleasure.” How we have all known this, eating in front of the television. The reverse can happen as well. Cancer patients who sampled a novel ice cream flavor prior to chemotherapy, with its attendant nausea, grew to dislike that flavor (more than the familiar flavors they liked). With liking for all foods diminished, patients were in little mood for novelty.
One way to avoid the treatment from negatively interfering with normal appetites, interestingly, was to provide a new “scapegoat” flavor—like Life Savers candy—during patients' normal meals. The scapegoat flavor, rather than the usual foods, absorbed the brunt of disliking. This plays into our tendency to want to like familiar foods and to dislike the novel.

In Pelchat's study, sponsored by a tea company wanting to see if Americans could acquire a taste for unsweetened teas, people even grew to like the tea more that did not have the glucose hit. Why? Simply because they were drinking it more than once. In 1968, the psychologist Robert B. Zajonc, in a profoundly influential paper, termed what he called the “mere exposure” effect: “
Mere repeated exposure of the individual to a stimulus is sufficient condition for the enhancement of his attitude toward it.” He was not actually talking about food, but exposure has come to be a central idea in food liking.
In one typical study, children as young as two sampled a collection of unfamiliar fruits and cheeses for twenty-six days in a row. When they were later given a choice between random pairs of the food objects they had tried, they chose the ones they had had more often—even when they had spat those out initially.

Try it, the old Alka-Seltzer ad (cheekily) promised, you'll like it. Parents do not usually have the patience of researchers (nor can they resort to gastric tubes).
They often abandon efforts to give their children new foods after three or four tries.
In an English study, one group
was asked to repeatedly eat spinach, not a huge delicacy in England. Another group was asked to eat peas, which are more liked. People began to like spinach a bit more, particularly those who disliked it at first. But liking for peas started high and stayed high.
People liked peas because they were already used to liking peas.

Exposure speaks to the idea that we like what we know. But to know it means we first have to eat it, even if we dislike it.
In one study, people began to like an initially disliked low-salt soup after having it just a few times (
the soup was not labeled “low salt,” because this in itself could be enough to negatively sway liking).
In another experiment, people ate canned ratatouille servings with successively higher levels of chili added. The hotter the burn, the more they grew to like it. George Orwell, in his 1946 essay “A Nice Cup of Tea,” predicted this kind of taste adaptation: “
Some people would answer that they don't like tea in itself, that they only drink it in order to be warmed and stimulated, and they need sugar to take the taste away. To those misguided people I would say: Try drinking tea without sugar for, say, a fortnight and it is very unlikely that you will ever want to ruin your tea by sweetening it again.”