A New Book Explains the Science of Smell

In June 2004, 55-year-old Luella Buchanan of Pleasant Hill, Calif., suffered an upper-respiratory infection. No big deal, right? That's what she thought, too. But after the sniffles subsided, for almost a year she had no sense of smell. The effect was dramatic. One day, when she failed to turn off a burner on the stove properly, she couldn't smell the leaking gas. (Her son, who dropped by four and a half hours later, noticed the fumes.) She stopped saving leftovers, as she no longer trusted her ability to detect rotten or rancid odors. Without aromas, food became a bland, tasteless mass, and life itself seemed equally blah. She was unable to enjoy the scent of coffee brewing, new-mown grass or the sweet smell of her baby grandson. Even her social life took a hit. She stopped inviting friends to dinner, as she had no way of gauging whether her chili was tasty or inedible. "It was like cooking with plastic food," she says.

Avery Gilbert is not surprised to hear this. But then, Gilbert is a self-described "smell chauvinist." He's also the author of a new book, "What the Nose Knows"—an entertaining romp through the science of smell. Gilbert knows the world of scents from the inside. In the 1980s, at a scientific research institute called the Monell Chemical Senses Center, he and a colleague were first to document that women's perception of odors is heightened during pregnancy (particularly during the first trimester, when a fetus is the most vulnerable to toxins that the mother might consume if not forewarned). More recently, he's been an "independent smell consultant" and designer of scents, ranging from perfume fragrances to odor concealers in kitty litter—a job he embraces enthusiastically. "How come we have Cigar Aficionado and Wine Spectator, but no Perfume Enthusiast?" he asks. "Why is there no independent critic—no Roger Ebert of scent?"

As Gilbert sees it, few people adequately appreciate their sniffers. Most of what we perceive as flavor in food does not come from the tongue, which picks up only the basic five tastes—sweet, sour, salty, bitter and umami (the savory taste in meat or broth). Instead, it comes from aromas of food being drawn up into the nose from the back of the throat, then exhaled through the nostrils. "Pinch the nose, and flavor disappears," he says. The nose even plays a role in mating. In a University of Texas study, Gilbert writes, "Men said T-shirts worn by women near the time of ovulation smelled more pleasant and sexy" than T shirts worn at other times.

Agreeable scents can summon the better angels of our nature. Psychologist Robert Baron tested people in fragrant locations like Cinnabon and the Coffee Beanery and found they were significantly more likely to help a stranger who "accidentally" dropped a pen or asked for change. And by putting us in a good mood, scents can encourage us to buy. That's why the Hershey's store in New York's Times Square pumps chocolate fragrance into the air and a Massachusetts furniture store wafts essence of bubble gum through the children's department. But unless you're selling food, scents should be subtle. "When a scent calls attention to itself, people feel obliged to decide whether or not they like it," he writes. "At that point, they're focused on the scent, not the store."

The curious thing about scents is how our perceptions of them change with the context. In one European study, participants were asked to evaluate an aroma. When presented with the words "body odor," they found the scent more objectionable than when the identical smell was paired with the phrase "cheddar cheese." Even more intriguing, wine tasters in one study thought they had been served two or three different wines when all that changed was the shape of the glasses. Perhaps this only confirms the traditional belief that the shape of a wineglass affects way aromas are collected and delivered to the nose. But Gilbert isn't so sure. He points to another study, in which a Cabernet actually smelled less intense in the traditional Bordeaux glass, while measures like fruitiness and oakiness were unaffected by glass shape. The participants, he notes, were blindfolded.

Gilbert laments that in our sanitized world, pungent smellscapes of the past are disappearing. A gleaming, modern brewpub is sterile compared with an old alehouse, with its "dark, hoppy yeastiness enlivened by the sawdust on the floor." Even the French, famous for their rich variety of stinky cheeses, are increasingly producing what Gilbert calls "fromage-blah." At the National Steinbeck Center, curators have tried to compensate by adding scents to the interactive exhibits for each of John Steinbeck's works—mangrove flower for "The Log From the Sea of Cortez," horse stable for "The Red Pony"—although the fishy smell of "Cannery Row" elicited so many complaints that they had to remove it.

Still, some scents may be poised for a comeback. For years, commercial flower producers have bred roses for traits like color, shape, disease resistance and vase life. Fragrance has been a casualty. Now biologist Eran Pichersky is attempting to isolate the scent-producing genes in one of the fragrant, noncommercial varieties. His goal: to transfer them into a scentless flower-shop rose. Other scientists are putting aromatic genes back into flavorless commercial tomatoes. Gilbert even speculates that gene therapy will one day help the elderly, whose sense of smell is diminished. If that day ever comes, it will be like recovering a whiff of youth.