Smellbound | Feature | Chicago Reader


Alan Hirsch and the Science of Scent

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Alan Hirsch leans forward across his cluttered desk. "We had one woman from Florida call who said she had an increased ability to smell," he says. "We said, 'Yeah, right,' but she said 'No really, I can smell a fire miles away.' So we told her to come here . . . and she was right! Her ability to smell was more than a hundred thousand times better than normal. Her ability to smell was about a hundred times better than your dog's. It approached that of a cockroach. . . . It was as if she could see in color, and the rest of us could only see in black and white."

Hirsch knows noses. Ten years ago, after finishing his psychiatry residency at Rush-Presbyterian-St. Luke's Medical Center, he decided his interest lay in olfactory disorders; today his Smell and Taste Research and Treatment Foundation sees about 1,000 patients a year, more than any other similar facility in the country. Hirsch's energy and almost boyish enthusiasm for his subject propel him through tangled but fascinating discourses on his research. On an exploration of the relationships between smell, taste, and human behavior, his train of thought has taken him from Play-Doh to penile blood flow to airborne Valium. And to Vegas.

Hirsch's route to Vegas began with an investigation into the connection between smell and the desirability of Nike shoes. He wanted to know if a pleasant smell in the vicinity of a product would inspire purchase. "What we did was we had the subject go into two identical rooms. In one room we had a nice floral smell and in the other room we had nothing, just filtered air." In each room was an identical pair of Nike shoes. After 30 seconds in the first room, the subjects were given a questionnaire about the shoes; then they went into the other room for an encounter with the second pair, followed by another questionnaire. "What we found," Hirsch says, "was that 84 percent of the subjects said they were more likely to buy the shoes associated with the mixed-floral smell."

But the results, intended only to gauge the effect of odors on marketability, suggested another conclusion, unforeseen and somewhat disturbing. During the experiment, the odor in the floral-scent room had dropped below levels considered detectable by the average person. "We tried to maintain suprathreshold levels, but many of the subjects' levels got so low they couldn't detect it. We tested the light, we tested the temperature, but it didn't make any difference. They said they were still more likely to buy the shoes in the room with the mixed floral smell."

Subliminal seduction, through the nose? Hirsch thought it was possible. Further experiments--at jewelry counters, for instance--supported the conclusion that pleasant odors at undetectable levels increased profits. But when he presented his findings to a group of colleagues at a meeting in Las Vegas, he ran into a dilemma. "Somebody got up and said, 'Dr. Hirsch, you're not causing people to spend more money in the presence of odors. What you're doing is causing the salesperson to be more friendly, and they're selling better!' It was a hard argument to argue against." Nonplussed, Hirsch spent the rest of the day wondering how to find a value-neutral vendor, how to "get rid of the salesperson." He found himself wandering the hotel's casino, surrounded, he suddenly realized, by a veritable forest of insensate pitchmen: slot machines.

After a three-week study Hirsch had the evidence he needed. The presence of the floral smell, even at subthreshold levels, dramatically increased the action of the handle. And as the level of odor went up, the increase was correspondingly higher: scented machines made up to 54 percent more money than odorless machines. It seemed to be further confirmation of the power of subthreshold odors to empty pockets, and the concurrent ethical and even legal questions surrounding subliminal marketing appeared to loom large. But Hirsch, the man who once wrote a letter to the New York Times warning that "research is now making strides to discover and manufacture odors that can be used . . . to control the consumer's emotions and thought processes," now saw things differently; in fact he found the study's results reassuring. "And I'll tell you why," he says, leaning back in his chair. "Businesses won't want to use subthreshold levels, because they have a greater effect at high levels!" Saved by the profit motive.

But this type of "market research" is just the tip of the Hirsch iceberg. His curiosity is especially sparked by the relationship between mental disorders and sensory acuity, and his research has suggested a reversal of the conventional wisdom. As far back as Freud, researchers have noted the connection between mental problems and disturbances in sensory perception and assumed that mental illness was the cause. Hirsch thinks that in some cases it may be the other way around; instead of viewing the loss of smell sensitivity as a symptom of the illness, he suggests that the loss of the ability to smell actually precedes and may in some ways trigger mental illness.

"We found that after people had lost their sense of smell there was a high incidence of GAD, or Generalized Anxiety Disorder, which is a form of long-term anxiety, and also dysthymia, a form of chronic depression," Hirsch says. "So we figured, well, why is it that when you lose your sense of smell you become anxious? Maybe there's some kind of free-floating Valium in the air that we all detect, and when you lose your sense of smell you can't detect it, and hence you become anxious." This leap of faith has revolutionary potential, but even Hirsch admits the difficulty involved in devising experiments to prove it. Persuading volunteers to offer up their sense of smell in hopes of developing an affective disorder promises to be a tough job.

Odors are volatile molecules suspended in the air. These molecules travel through the nostrils to land behind the bridge of the nose on the olfactory epithelia, two mucous-coated patches about the size of a dime. There the molecules bind to receptors--i.e., neurons--on the olfactory nerves, which carry the message straight to the brain's olfactory bulbs. This direct path to the brain makes smell unique among the senses. The cornea and the eardrum both act as physical barriers between neurons and the outside world; odors, in effect, land directly on the brain's doorstep. And what is often perceived as taste is actually mostly smell, since the tongue is only capable of discerning four flavors--salty, sweet, bitter, and sour. Any shading beyond this narrow repertoire is courtesy of the nose.

Inside the brain, structures called glomeruli sort out the complexities of an odor and send messages on to the limbic system--the brain's center of emotion and also of memory, which helps explain the singular link between smells and nostalgia. The limbic system activates the hypothalamus and the pituitary gland, which produce hormones that control sex, appetite, and other functions.

It's the connection to these basic functions that gives smell hegemony among the senses in many forms of animal life. Ants, for instance, leave a trail of pheromones to establish pathways between the nest and food sources. Without the trail they're lost; rub your finger across the route of a train of ants on the sidewalk and watch the chaos. Leaf-cutter ants use a trail pheromone so potent that one milligram is enough to lead a small column around the world--three times. Rats and many other mammals would be unable to identify their young without smell, let alone find a mate. And when your cat rubs its whiskers against your leg, it's not just being cuddly; it's also smearing you with feline hormones secreted from glands near its eyebrows.

In humans, smell has been sublimated in favor of sight and touch, senses more useful to creatures with the upright posture and manual dexterity bestowed by evolution. But vestiges of the power of smell remain, finding expression in phenomena both mysterious and feral.

The twitching nose of the animal still lurks beneath the countenance of the civilized human being. The peculiar smell of your neighbor's house is a type of "nest" odor, found in animals from ants on up. The neighbors can't smell it because it's theirs; your house probably smells just as funky to them. Women living in close quarters often find their menstrual periods have become synchronized, a result of the subliminal detection of hormones in each other's sweat. Similarly, a woman living with a man will often develop more regular periods due to exposure to male pheromones. Our aversion to "bad" smells originated as a safeguard against real physical threats. Rotting meat smells like death. Spoiled fish smells like poison. These are issues of survival, not just aesthetics.

And yet smell research is something of a biological backwater. It's still not fully understood how odor molecules are "read" by the olfactory epithelia, for instance, and until recently there was no answer for a question that is central to understanding smell: what is it that prevents odors from lingering in the nose, piling on top of each other, creating olfactory havoc? It's now thought that after the volatile molecule has sent its message, enzymes similar to those used by the liver to detoxify blood flood over the olfactory epithelia. Within a second or so, the enzymes have dispersed the odor molecules, cleansing the system and preparing it for the next smell. But many mysteries remain, and laboratories devoted to unraveling them are few and far between.

There are two ways to get to the offices of the Smell and Taste Foundation in Water Tower Place: past the "mixed floral" aroma of the flower shop near the door of the east lobby or through the maelstrom of Marshall Field's or Lord & Taylor's perfume counters. The foundation's modest suite on the ninth floor--a reception area, three examining rooms, and Hirsch's office--has a terrific view of Michigan Avenue.

It was on this busy street that Hirsch and his colleagues once quizzed passersby about the smells of their youth. The results, showing what odors reminded volunteers of childhood, were published in the Psychiatric Times in 1992. Categorized according to the age of the subject, they revealed a predictable shift as the subject's age diminished--from tweed, Cracker Jack, meatballs, and manure to Play-Doh, rubber fish bait, candy cigarettes, baby aspirin, Windex, and tuna casserole. But what seemed to be harmless, even pleasant whiffs from memory lane held some ominous news for Dr. Hirsch. Call it the Cut Grass Syndrome.

Hirsch found that people born before 1960 who described grass as a nostalgic smell also remembered having a generally happy childhood, but the cut-grass group born after 1960 said they had been unhappy. "I asked [the second group], "What is it that the smell makes you recall?"' Hirsch says. "They said it made them recall being forced to cut the grass. So what we were seeing is a change in perception. Whereas before it was viewed as a responsibility, now it's viewed as a chore." Unsure of how to handle this information, Hirsch didn't include it in the published report. The finding takes its place among the many enigmas involved in his research.

Others have included a woman who complained of an omnipresent smell of vinegar; CAT scans showed nothing unusual, but the smell persisted for years. Or the patient whose growing conviction that he didn't smell "right" caused him to begin to withdraw socially; later he came to believe that he was dead inside, and explained the stench he smelled emanating from every pore as the result of internal putrefaction. These are examples of olfactory hallucination, or phantosmia, and they are usually either indicative of an underlying mental health problem or the result of trauma to the limbic area of the brain. Hirsch regularly treats patients with phantosmias. As a matter of fact, he had one once himself.

He was on his way to surgery as a med student in Ann Arbor when a car knocked him off his bike. When he came to he smelled cigarettes--everywhere. A nostalgic odor, perhaps, the result of being deprived of cigarettes while in the hospital? "No," Hirsch says, "I've never smoked." The smell came from nowhere and subsided after a couple of weeks, though his sense of smell is still diminished.

This episode, fateful though it may have been, had no direct bearing on Hirsch's becoming a smell doctor. He found his calling through a mistake he made in med school. While "compulsively" administering full neurological exams to all of his psychiatric patients, Hirsch made a startling discovery: none of them could smell. "I said, "Gee, maybe this is a way of understanding psychiatric disease. Maybe this is a window of understanding!' But what I was too stupid to realize was that the reason they couldn't smell was because of all the drugs they were on. And if any of my professors had told me that beforehand, I probably never would have become interested in smells."

A cigarette, drawn from a fresh pack, smells of raisins and vanilla. This is not an irony supplied by nature; it is an additive supplied by the manufacturer, the result of well-funded research by tobacco companies into how to make a carcinogen smell nice. If the heavy industries surrounding the southern tip of Lake Michigan could figure out a way to make their effluvia smell like cocoa or baking bread, you can bet they would. You know it's dangerous to smoke cigarettes or live downwind of a chemical factory, but the actual threat posed to you by exposure to such poisons is not necessarily reflected in the way each poison smells. If USX could mask their toxic waste with a fresh 'n' clean piney smell, it would still be bad for you to inhale. Crud by any other smell would still be crud. Of course, you know that.

But companies like R.J. Reynolds hope you'll forget that if your nose tells you to. As sociologist Anthony Synnott has pointed out, odor "is a significant component of our construction of reality and our construction of moral reality. The fundamental hypothesis is simple: what smells good, is good. Conversely, what smells bad, is bad. The phrase 'Ummm! That smells good!' neatly equates the physical-chemical and symbolic-moral realities." And reality is slippery. The food-additive factory at Irving Park and Western may give the neighborhood the sweet smell of butterscotch or wild cherry, but who knows what really goes on inside?

But factories and cigarettes are easy. Let's say instead that John Smith, citizen, is stuck in a mid-July rush hour on a CTA bus. The guy wedged next to him is holding the balance bar, arm raised, and he just plain stinks. Chances are that our citizen will end his ride with a strong opinion of his assailant: his personal habits, life-style, and moral character. Now suppose the offender belongs to a different racial group, or nationality, or social class than Mr. Smith. For Synnott, the implications are immense: "We judge people the same way as we judge food and the environment. If a person smells 'bad,' or deviates from the olfactory cultural norm . . . the aromas are converted from physical sensations to symbolic evaluations." John Smith's antagonist could be a Nobel laureate or a career criminal, but his smell is evidence enough to convict.

Of course, the issues go beyond BO on the bus. If you're fresh off the plane from Cairo you may wonder why every American you encounter is ashamed to meet you. And every American you meet may be wishing you would just back off a little. According to anthropologist Edward T. Hall, Arabs customarily "make more use of olfaction and touch than Americans. . . . Arabs consistently breathe on people when they talk. . . . To smell one's friend is not only nice but desirable, for to deny him your breath is to act ashamed." A misused phrase or a blunder at the dining table may inspire a condescending glance, but an offensive smell or habit goes straight to the limbic system. Xenophobia stinks.

Judgments based on smell have found particularly colorful expression where race is involved. George Orwell wrote, "The Chinese . . . say that a white man smells like a corpse. The Burmese say the same--though no Burman was rude enough to say so to me." Synnott says that the Japanese used to describe Europeans as bata-kusai, which he translates as "stinks of butter." Thomas Jefferson's racist characterization of the odor of African American slaves as "disagreeable" has been countered by Malcolm X's reference to "the different way that white people smell." Synnott sums it up: "We do sniff each other out, literally as well as figuratively."

But people aren't only interested in how other people smell. We've been enhancing our own odors for thousands of years in an effort to smell good--and therefore be good. The modern big-money perfume industry targets women with obvious--and frequently ludicrous--pitches. There are inscrutable fantasy commercials that simultaneously offer women everything and nothing at all. Then there are fragrances made for men but aimed at women, mysteriously able to strip them of every shred of autonomy and self-control with just one whiff. And then there's the fear angle, which Germaine Greer has summed up in her attack on those who "invent[ed] the problem (at one and the same instant as its solution) of vaginal odor. . . . After all, it's not as if the streets had been littered with those overcome by vaginal fumes."

Scents are used by industry to enhance the consumer appeal of everything, even products that are allegedly "unscented." A trip to your grocery store involves an all-out olfactory attack, but you're probably unaware of it unless you have an exceptionally sensitive nose. One of the few instances of a "bad" smell being intentionally added to a product is the infusion of a group of chemicals called mercaptans into natural gas, which is ordinarily truly unscented, so gas leaks won't go unnoticed. Unfortunately, a recent survey indicates that older people's reaction to mercaptans is less negative than other groups. A new, probably worse, natural gas smell may be in the air soon.

Hirsch has quite a collection of smells. In one of the three examining rooms at his office he offers a sample from a cardboard box holding a jumble of mysterious-looking dark vials. "Guess what this one is," he says. A sniff. Oranges? Hirsch smiles, with just a trace of condescension. "Pretty close. Pink grapefruit. Here, I got another good one . . . " Pink grapefruit hangs in the air while he rummages around in the box. He uncaps the next vial: grassy, penetrating, familiar, but impossible to place. Hirsch smiles again. He's enjoying himself. "Parsley," he says. "Not too many people get that one." Essence of Parsley mingles with Eau de Pink Grapefruit as we turn to some unintentionally bad samples: "smoky barbecue," a nose-wrinkling blend of rotting meat and burnt sugar, and "cheese pizza," stale and vinegary. By now the room is foul with antagonistic odors. Hirsch switches on a small yet powerful-sounding filtering machine.

The individual responsible for the nastiness of "cheese pizza" may well have been a master chef, if the results of a recent Hirsch study are correct. Searching for a group of subjects with a high sensitivity to smell and taste, Hirsch quite reasonably settled on a sample of chefs from four-star restaurants. Surprisingly, they all turned out to be significantly less sensitive to both smell and taste than the average person. Hirsch was baffled, but as with most of the mysteries uncovered by his research, he has a theory. "Let's pretend for a second that chefs had a great ability to smell," he says. "Remember, 90 percent of taste is the ability to smell. Now, the person comes along who can afford these four-star restaurants. Who are they? They're primarily businessmen. They're all successful, so they're probably older, which drops their sense of smell. They drink, that drops their sense of smell. They smoke, that drops their sense of smell. So they sit down . . . the chef brings out the food, the patron takes a bite, and he says, 'This food is bland. Get rid of the chef!'" Hirsch leans back and takes a rare pause to savor the beauty of his logic.

Food also figures in Hirsch's research into the effect of smells on sexual response. "It's too bad you were a day late, we would have used you," he laughs. "In the study we did earlier with medical students, as a pilot study, the only odor we found that effectively increased penile blood flow in men was the smell of cinnamon buns. Whether that was just because medical students are always hungry we're not sure. So now we're doing a study of the general population." The results of the sex study, Hirsch says, could be used for everything from treating impotence to rehabilitating chronic sex offenders. It could mean the end of stickybuns in the hoosegow. Studying women's sexual responses is next, but results may be slow in coming. Hirsch says that adapting the experiment to female physiology is difficult and expensive.

After that Hirsch will study the links between smells and claustrophobia, and after that could come, it seems, just about anything. Down on Michigan Avenue crowds hustle by, oblivious to the whirlwind of stimuli surging across their olfactory epithelia, completely unaware of the associations and moral evaluations being coaxed out of their limbic systems by their honkers. The lowly nose: often blown, rarely loved, but always on the job.

Art accompanying story in printed newspaper (not available in this archive): photos/Charles Eshelman.


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