Tasty
Authors: John McQuaid
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For Mom
CHAPTER 1
The Tongue Map
E
arly in his psychology career, Edwin Garrigues Boring often used himself as a guinea pig. As a graduate student at Cornell University in 1914, he swallowed feeding tubes to measure how his esophagus and stomach responded to different foods, and sliced a nerve in his own forearm in order to document its gradual regrowth. In 1922, just before Boring was to start a teaching job at Harvard, he was struck by a car on a rainy night. He lay in a hospital bed for six weeks with a fractured skull and short-term memory loss, forgetting his conversations with visitors within a few minutes. After he recovered, Boring used this experience to analyze the nature of awareness, pondering whether someone living in an eternal present was truly conscious.
This hands-on sensibility helped make Boring one of the twentieth century's most influential psychologists. It wasn't by virtue of any single theory or discovery. (Though he did popularize a minor curiosity, the “Boring figure,” an optical illusion in which a slight shift in perspective flips the image of an old woman's face, as perceived by the eye and the mind, to that of a young woman's head.) Instead, Boring made his mark by changing the popular conception of psychology itself. When his career began, the field was a hodge
podge of disciplines, equal parts philosophy, therapy, and lab experimentation, each with its own approach and terminology. From his influential perch at Harvard, Boring pushed to make it more consistent and rigorous, to have it hew more closely to the scientific method. He believed a scientist was obligated to relentlessly scrutinize and measure his own sensations, grounding all findings in direct observationâa tenet of the philosophy known as positivism. This was the closest science could possibly get to the truths about reality it aspired to capture.
But there was a point in his career when putting these beliefs into practice could have averted a major scientific misunderstanding, and Boring failed spectacularly. The mishap involved the nature of taste. By the 1940s, Boring had become an accomplished historian, chronicling the emergence and evolution of modern psychology. His 1942 volume,
Sensation and Perception in the History of Experimental Psychology
, is still considered a magisterial survey of the science of the human senses stretching back to Sir Isaac Newton's seventeenth-Âcentury studies of light and color.
Boring covered taste and smell in a relatively brief chapter in the book, twenty-five pages out of seven hundred. Midway through it, he reviewed an experiment done in 1901 by David P. Hänig, a German scientist. Hänig had brushed sweet, salty, bitter, and sour solutionsârepresenting the four basic tastes, important components of flavorâon different areas of the tongues of volunteers, and then asked them to rate their relative strength. He found the threshold for detecting each taste varied around the edge of the tongue. The tip, for example, was more sensitive to sweetness and to salt than was the base.
It wasn't clear what this meantâif anythingâand the
differences were very small. But Boring found this notion interesting and went to some lengths to illustrate it. He borrowed the data from Hänig's study and turned it into a graph. The graph was just a visual aid; it had no units, and its curves were impressionistic. But the result was thatâperhaps to dramatize the point, or perhaps inadvertentlyâBoring made small differences in perception appear huge.
The wayward chart became the basis for a famous diagram of the tongue, divided into zones for each taste: The tip is labeled sweet and the back bitter. Along each side, salty is close to the front, and sour is behind it. The center is blank. Linda Bartoshuk, a professor of psychology who has studied this map's origins, believes it came about through a game of “telephone”: First, Boring exaggerated Hänig's findings. Then researchers and textbook editors misinterpreted Boring's graph, using the peaks of its curves to label specific areas on the tongue. A final round of confusion produced a diagram with taste boundaries clearer than those on a world map.
The tongue map offered a simple explanation for how the tongue processed tastes, a phenomenon everyone knew intimately. Teachers embraced it. Generations of elementary school students sipped and swished water spiked with either sugar, salt, lemon juice, or tonic water in a classroom experiment designed to dramatize the tongue map. Like air raid drills or dodgeball, the tongue map became a feature of postwar American schooling and lodged itself in the popular imagination.
However, these demonstrations no doubt confused more children than they enlightened, as many found they couldn't detect the supposedly dramatic taste gradients. Even as the tongue map took on the mantle of conventional wisdom, research revealed that it wasn't merely an exaggeration or
Âmisinterpretation but totally wrong. In 1973, Virginia Collings of the University of Pittsburgh repeated Hänig's original tests. Like him, she found very limited variation in the tongue's taste geography. In the 2000s, more advanced tests showed that all five tastes (“umami,” or savoriness, was recognized as a fifth in 2001) can be detected all over the tongue. Every taste bud is studded with five different receptor proteins, each tailored to detect molecules of one of the basic tastes.
Had Boring done some taste testing himself instead of interpreting Hänig's forty-year-old data, he might have noticed the problem with his graph. Instead, he launched one of the more widely disseminated bits of scientific misinformation in history.
The old diagram has lost much of its cachet in recent years. But it still lingers in some areas of the culinary world, including coffee and wine tasting, which value tradition and continuity as much as science. Claus Riedel, the Austrian glassware designer, used it to create wineglasses whose unique curvature is intended to deliver each sip to the right place on the tongue to release the full flavor. (Riedel died in 2004; since then, his son and successor Georg Riedel has acknowledged that science undermines the tongue map, but maintains the glass designs work.) Boring died in 1968, before the map had been discredited. That he made a fundamental error about the nature of one of the senses, which he considered the building blocks for understanding both the mind and the universe, is an irony that he would doubtless have found mortifying. It was no mere miscalculation, but a basic error about a universal human experience. Everyone knows the gratifying “Mmm” of sweetness and the stark taste difference between a pinch of salt and a fistful. Cheesecake makes the brain explode with plea
sure. The complex tastes in coffee are a global obsession. Recipes distill entire cultures down to a single sensation. Flavor is one of a very few things that make day-to-day existence not just survivable but consistently enjoyable.
Why did this happen? Mere carelessness doesn't seem like an adequate explanation of Edwin Boring's disregard for his positivist philosophy, the foundation of his life's work; nor does the fun of the tongue map experiment completely account for its persistence given that it never really worked. Boring's mistake may be flavor's version of the Freudian slip, an apparently superficial error that reflects hidden conflicts.
One reason for the befuddlement is that for thousands of years, scientists and philosophers have viewed taste and flavor as less-than-worthy subjects for study. The ancient Greeks considered taste to be the lowest and grossest of the senses. Vision can discern the subtleties of high art or the smile of a loved one, but taste's mission is simple: to distinguish food from everything else. The Greeks thought the temptations it posed in carrying out that mission clouded the mind. In his dialogue
Timaeus
, Plato wrote that the sense of taste was caused by the varying roughness or smoothness of “earthy particles entering into the small veins of the tongue, which reach to the heart.” The heart was the seat of the baser bodily sensations, while thought and reason occupied the “council chamber” of the brain. Of course, food was headed for the belly, a ravenous beast knocking about far below the deliberating council: “the belly would not listen to reason, and was under the power of idols and fancies.”
Plato practiced what he preached: in his
Symposium
, guests gather for a banquet, but decline food or drink in order to keep their minds clear for the discussion on the nature of love.
These biases became a fixture in thought about the senses
for centuries. The German philosopher Immanuel Kant wrote in the eighteenth century that flavor was too idiosyncratic to be worthy of study. To Kant's eye there were apparently no universal principles governing it, like those governing the behavior of light. Even if there were, they could not be derived from observation, because there was no way to observe the mind. Taste would always elude us. Kant's contemporary David Hume disagreed, arguing that good taste in food was tied to good taste in art and all things. But it was Kant's more skeptical attitude that persisted.
These withering assessments overlook a great deal, and they reflect a certain discomfort. Flavor embodies the basic savagery of being an animal, devouring the flesh of other animals and plants in order to stay aliveâand loving it. In flavor the order of civilization momentarily disappears and is replaced by carnage. Confronting this part of human nature is unnerving. Eating and drinking are also forms of intimacy that are, in their own way, as powerful and unsettling as sex; after all, they involve taking something inside the body, many times a day, with flavor as a seducer. Flavor is a conscious manifestation of ancient, inexorable drives that make life possible. Sigmund Freud believed the central drama of life sprang from the sex drive. But the drive for sustenance, which runs on a similar cycle of craving, pleasure, release, and satisfaction, maintains a more powerful, consistent grip on our lives and motivations.
The other problem in studying flavor is the basic inscrutability of a phenomenon that unfolds entirely within the body, brain, and mind. Vision, hearing, and touch are “shared” senses. We all see (or think we see) the same shades of color, hear the same sounds, feel the same textures with our fingertips. This gives scientists a common frame of reference with
which to conduct experiments, collect data, and compare notes on these phenomena and the senses that perceive them.
There is no such shared reality with flavor. Like light and sound, the chemical components in food and drink are objective, measurable quantities. Yet the perceptions of them vary wildly from person to person: There are delicate sensibilities and dull ones. Foods beloved by some are despised by others. Tastes vary by culture, by geography, even by one's mood. A scene from
Don Quixote
captures these subtleties. Sancho Panza, the slovenly, loyal squire, boasts to strangers that a sensitive palate (a sign of good breeding) runs in his family. He tells the tale of two relatives judging a fine wine in a tavern. One sips it, swishes it in his mouth, and says it's wonderful, except for the slight taste of leather. The other takes a drink. It's excellent, he says, except for that off hint of iron. The barflies mock the relatives for putting on airs. But when the wine cask is emptied later, the tavern owner finds an iron key on a leather thong.
Such differences of perception offer hints at flavor's inner workings, a secret world lying just under the surface of everyday experience, waiting to be cracked open. But this subjectivity is also exactly what makes it so difficult to formulate general principles about flavor chemistry or perception. Newton devoted years to the study of light and color perception, and founded the science of opticsâdemonstrating, among other things, that white light was not the absence of color but a blending of all colors. But there was never a Newton of tasteâno Enlightenment-era scientist to revolutionize the field and set it on a path to a modern understanding.
The combination of inaccessibility and unease conspired to keep taste and flavor on the scientific margins for most of the past two thousand years. The ancient Greeks first formu
lated the idea of “basic” tastes as irreducible elements, the atoms of flavor. Some of the earliest known attempts to explain taste were made by the physician Alcmaeon, who lived in the Greek city of Croton in Italy and wrote sometime between 500 and 450
BC
. He thought the tongue, like the eyes (and nose and ears; for some reason, touch was left out), had its own
poroi
, or channels, that transmitted perceptions, like barges delivering amphorae of wine, to the brain. That's exactly what nerves do. In the fifth century
BC
, the philosopher Democritus declared that the perception of taste depended on the shape of individual atoms, the postulated smallest units of matter: sweet atoms were round and relatively large, so they rolled around on the tongue, salt atoms were shaped like isosceles triangles, and pungent ones “spherical, thin, angular, and curving,” prone to tear the tongue's surface and generate heat through friction, which explained the irritation they caused.
With only minor variations, this conception of flavor has been a staple in most societies and civilizations from then to now. Traditional Indian medicine, known as Ayurveda, Sanskrit for “life-knowledge,” employs combinations of sweet, sour, pungent, bitter, salty, and astringent tastes to combat illnesses. Its weight-loss diet prescribes foods that are pungent (a product of the elements fire and air) or bitter (air and ether) to combat an excess of
kapha
, or phlegm (earth and water). Carl Linnaeus, the Swedish botanist who in the eighteenth century invented the modern scientific system for naming species and classifying life, identified the basic tastes as sweet, acid, bitter, saline, astringent, sharp, viscous, fatty, insipid, aqueous, and nauseous. The idea behind the tongue map, that nature has cleanly divided the tongue's territory into taste regions, grows out of this tradition. It is simple and appealing, like the nineteenth-century phrenology dia
grams that mapped various mental capacities onto areas of the skull. But in recent years, flavor's once mysterious, closed-off domains have begun to open up. Scientists employing new tools and technologies have deepened our understanding of flavor, helping it to shake off its second-class status among the sensory phenomena and placing it squarely in the vanguard of the study of human biology.