What the Nose Knows: The Science of Scent in Everyday Life (3 page)

Ingredient Voice assumes perfumer-level familiarity with more than a dozen raw materials, when in fact few civilians have ever smelled orris root or vetiver. Reciting a list of ingredients gives an illusion of precision. Even perfumers don’t think of
Beautiful
as a list of ingredients; they might think of it as a big, complex floral type with an ambery warmth. Ingredient Voice doesn’t help the casual shopper.

In contrast, Imagery Voice is all about atmospherics. The drama of seduction, passion, and mystery makes Imagery Voice the natural language of brand marketers and ad agencies. Listen to an actual vice president of marketing discuss a new men’s cologne with a cosmetics industry trade magazine: “It’s intended to target a young, stylish, hip, contemporary kind of guy.” So far, so good. Aging, badly dressed nerds aren’t known for buying a lot of cologne.

“The positioning of [the new brand] is really based all about capturing the pulse and energy of the city.” Reasonable enough—discretionary consumer dollars don’t chase listless, slow-moving, rural scents. But what does the new scent smell like? Hearken to the Imagery Voice:

The fragrance notes themselves are city inspired, in that the top notes we describe as being powered by “living liquid air.” It’s fused into a matrix of metal aldehydes and it captures the feeling of shiny steel and glass in a modern urban environment. It is very fresh and almost metallic on top; then it dries down to warmer, more sensual suede and woody notes on the bottom.

That’s an impressive prose poem. Buried in it are two actual smells: suede and wood. Suede is fairly specific—one imagines the smell of a supple jacket or new pair of shoes. Woody, on the other hand, covers a lot of territory: pine, oak, cedarwood, redwood, cypress, and don’t forget sandalwood. If Mr. Young Stylish and Hip wants to know what this new cologne smells like, he’s just going to have to smell it for himself.

Imagery Voice combines ordinary adjectives (fresh, woody) with technical terms (aldehydes) and envelopes them in emotional verbiage (“the feeling of shiny steel”). The result is the marketing equivalent of a Jell-O mold at a church dinner.

N
OTICEABLY ABSENT
from the world of perfume is the identifiable voice of the independent critic. There is no Roger Ebert of scent. A scientific polymath and self-appointed expert named Luca Turin once tried his hand as a freelance perfume reviewer. Turin is serious about the aesthetics of fragrance and not a shill for any manufacturer. But his capsule reviews tend to be highly stylized. Here’s a whiff: “
Après l’Ondée
evolves only slightly with time: its central white note, caressing and slightly venomous, like the odor of a peach stone, imposes itself immediately and retains its mystery forever.” Turin makes
Après l’Ondée
sound both impossibly abstract and off-puttingly tactile. Meanwhile, a reader still doesn’t know what it smells like.

Perfume wearers need a style of commentary that blends the aesthetic and the technical, like the road tests in
Car and Driver
that talk about sporty handling and trunk space in the same paragraph. In 2006 the
New York Times
tapped Chandler Burr as its first-ever perfume critic. Burr rates perfumes with a conventional five-star scale and a writing style that tilts heavily toward the aesthetic: “This is the scent of the darkness that inhabits a Rubens, a warm, rich, purple blackness;
Pomegranate Noir
is like a box of truffles with the lid on, sweet bits of darkness, waiting.” (OK, but what about the horsepower and mileage?)

Practical-minded perfume fans might prefer “Andrew,” who pens cheeky analysis for the English newspaper
Metro.
Here’s his take on
Live Luxe
by Jennifer Lopez: “It’d take a very brave/mad woman to wear this one. Ridiculously sweet and fruity, this is the fragrance equivalent of going out dressed as Carmen Miranda with a fruit cocktail poured down your cleavage. Invigorating but not for use in an enclosed space.” Andrew recommends it “[f]or ladies who like to make an impression.”

How come we have
Cigar Aficionado
and
Wine Spectator,
but no
Perfume Enthusiast
? This is a magazine publishing niche waiting to be filled. In the meantime, perfume bloggers are popping up all over the Internet: IndiePerfumes, Anya’s Garden of Natural Perfumery, SmellyBlog, Scentzilla, to name just a few. As elsewhere in the blogosphere, this evolving community is a mixture of the personal and the professional, the serious and the whimsical. But the passion for fragrance is always there. These writers are pioneering new ways of describing scent. I think their efforts may produce a vibrant, robust, and very useful way of organizing the world of perfume.

The Big Enchilada

Perfumes, flowers, and wine occupy the sunny heights of the smellscape. Beyond lies the Dark Side, a swampland reeking of burnt rubber, rotten eggs, and the silent but deadly guy on the No. 33 bus. Few people aspire to study stench—there are no maestros of malodor. And yet, if we are truly to understand the sense of smell, we must account for the whole of it: the good, the bad, and the ugly. Where is the Universal Classification of Smell?

According to conventional wisdom, all major smell classifications can be traced back to the eighteenth-century Swedish naturalist Carl von Linné (1707–1778), known as Linnaeus. Linnaeus was the Big Daddy of scientific classification. In fact, he was a little obsessed with the topic: he classified plants and animals, rocks and sea creatures, and even his fellow scientists. Far from being a muddy-boot field biologist, Linnaeus was a bookish desk-jockey more concerned with defining the single “type” of a species than with the extent of natural variation. For this reason, some historians view him as a rigid essentialist who held back progress in the life sciences for decades. Still, his decision to assign a two-part Latin name to every species—something he regarded as a minor innovation—was a stroke of genius, and it became the basis of all modern taxonomy.

Linnaeus is widely credited among psychologists with inventing the first scientific classification of smells. Very few of them, however, seem to have read the actual treatise, published in 1752. Its Latin title,
Odores medicamentorum,
translates as “The smells of medicines,” and this is the first big hint that Linnaeus’s primary interest was not smells, but the medicinal properties of plants. He believed he could predict the therapeutic effect of a plant from its odor. To his way of thinking, nonsmelly plants were medically worthless, while strong-smelling ones had great pharmaceutical potency. Similarly, he believed sweet-smelling plants were wholesome, nauseous ones were poisonous, spicy ones were stimulating, and “noisome” ones were “stupefying.” These effects were due to plant smells acting directly on human nerves. You can be forgiven if the views of Sweden’s greatest scientist sound to you like those of a New Age aromatherapist in contemporary Santa Monica.

In grouping medically useful plants by odor, Linnaeus came up with seven classes that translate as fragrant, spicy, musky, garlicky, goaty, foul, and nauseating. His only concern was using smell to classify natural medicines; he did not intend to create a universal classification of all smells. In fact, he had little interest in smells
as
smells. (This explains the absence of such obvious odor categories as floral, fruity, woody, and leafy green.) Despite his focus on medical properties and his neglect of sensory qualities, European scientists viewed Linnaeus as the first scientific classifier of smells, and the results were a disaster—it sent smell researchers on a wild-goose chase that lasted for two centuries.

The next scientific smell classifier emerged toward the end of the nineteenth century. The Dutch physiologist Hendrik Zwaardemaker (1857–1930) was, by his own account, not particularly interested in smells. His lack of feeling for the topic shows in his work, where his main contribution was to add two new classes (“ethereal” and “empyreumatic”) to those of Linnaeus and to create subdivisions within each class. The new version was complicated and made little sense as a comprehensive classification. (He was, after all, cramming every smell in the world into categories meant to organize only smelly medicinal plants.) Zwaardemaker labored to explain his system, but his tedious cross-referencing of previous classifications has all the prose sparkle of the IRS tax code. Like the system it expanded on, Zwaardemaker’s classification was based entirely on one man’s opinion, rather than on experimental data.

The German physiologist Hans Henning (1885–1946) relentlessly attacked the inconsistencies and absurdities in Zwaardemaker’s classification. He took aim at Zwaardemaker’s preference for lifting odor descriptions from novels and literary works rather than from the direct experience of his own nose. Henning insisted that sensory experience was superior to empty intellectualizing; his motto was “just smell it.” His own classification, proposed in 1916, had two very important selling points: it was based on empirical data, and it came with a ready-made visual representation, the “odor prism.” The image was a compelling one, orderly and neatly geometric. The six corners of the prism were each assigned a specific odor quality. Henning claimed that any odor could be located on the surface of the prism; its distance from any corner indicated the relative contribution of that odor quality.

Unfortunately, Henning overplayed his hand. The clean geometry of the odor prism proved irresistible to the scientific psychologists in America, who tested its feasibility in laboratories at Harvard, Clark, and Vassar. Initially enthusiastic, the Americans soon found his theory to be cumbersome and too vague to yield testable predictions. In their hands, it produced inconclusive results. Henning’s initial theory was based on work with only a few experimental subjects; it now became clear that those subjects were extremely, if not suspiciously, consistent in their responses. (Wide person-to-person variability is a hallmark of odor perception; it’s unlikely that randomly selected sniffers would agree as precisely as Henning’s trio did.) In retrospect, there was always something too neat about Henning’s idealized prism: its geometric elegance is undeniably appealing, but few areas of human experience are less linear than smell.

The dismantling of the odor prism by American psychologists ended the European tradition of armchair smell taxonomy. The search for a Universal Classification of Smell shifted entirely from philosophical reasoning to experimental research, and with it momentum crossed the Atlantic for good. Although as outmoded as the buggy whip, the odor prism persists in contemporary encyclopedias and textbooks, a testament to its iconic power.

I
T WAS FRUSTRATION
with Henning’s prism that led the Americans Ernest Crocker and Lloyd Henderson—of the “10,000 odors” estimate—to invent a new system of smell classification. They began by selecting four “elementary odor sensations”: fragrant, acid, burnt, and caprylic. Then they assembled a set of odors to serve as reference standards, by means of which any smell could be rated on a scale of 0 to 8 for each of the elementary sensations. Rose, for example, was rated 6 on fragrant, 4 on acid, 2 on burnt, and 3 on caprylic. Those four numbers (6423) became, presto change-o, a digital identifier for that particular smell. In the same way, vinegar was 3803 and freshly roasted coffee was 7683. A numerical specification of sensory quality is not that outlandish; the Pantone color standards, for example, use numbered samples to let graphic designers and printers communicate accurately.

The Crocker-Henderson system had wide appeal because it was based on empirical data and an open set of standards: anyone could play. Following its publication in 1927, the system was quickly commercialized; the complete set of reference odors could be ordered from Cargille Scientific, Inc., in New York City. It was soon being used by distillers, soap companies, the U.S. Army, and even the Department of Agriculture. Sensory psychologists initially gave the system positive reviews, but in 1949 researchers at Bucknell University dealt it a stunning blow. They found that untrained people couldn’t sort the thirty-two reference odors into anything resembling the four elementary sensations postulated by Crocker and Henderson. Further, people were unable to arrange the eight odors within an elementary group in order of intensity. Because the Crocker-Henderson system was premised on elementary odors and intensity-graded smells within them, the new findings effectively undermined its logic. User enthusiasm vanished and the system eventually faded away.

A
NOTHER BURST OF
innovation in odor classification took place in the 1950s and 1960s when chemist John Amoore observed that people who were odor-blind to the stinky-feet smell of isovaleric acid were relatively insensitive to similar smells. He proposed that “sweaty” was a primary odor in the same way that red is a primary color. Amoore sought out molecules with similar shapes and smells that he thought might be the basis of other primary odors. (He eventually proposed seven of them: camphoraceous, musky, floral, pepperminty, ethereal, pungent, and putrid.) While he did succeed in finding other instances of selective odor blindness, Amoore’s notion of primary odors did not hold up under rigorous sensory testing. In the end, the structural features of a molecule are not a reliable guide to the psychological realities of odor categories.

The latest attempts at odor classification use a technique called semantic profiling, an approach pioneered by the fragrance chemist Andrew Dravnieks in the 1960s, and still used today. Researchers hand people a long list of smell descriptors and have them check off as many as apply to a given odor sample. The hope is that with enough descriptors, smells, and statistical analysis, a pattern will emerge. And indeed patterns do appear—it is possible to point to groups of odors that share similar descriptions. The trouble is, this leaves us back where we started from—odors are described similarly because they smell similar. What we really want to know is, Why do they smell similar? For now, scientists are stumped—the molecular structure of odors isn’t the answer, nor can we conjure categories from lists of adjectives. As a result, researchers today are reluctant to propose anything like the grand classifications of the past.