The sense of smell

If you’re like most people, when you’re asked to list the five senses, your order will be something like: sight, hearing, touch, taste and–oh, yeah–smell. Like Rodney Dangerfield, smell “can’t get no respect.”

But all that may be changing. And the Japanese, as in so many other areas of technology, are leading the way–by a nose.

A company called S. Technology Centre-America has developed (try to say this quickly five times in succession) an Aromatherapeutic Environmental Fragrancing System, which broadcasts special smells through air-conditioning ducts of buildings in an effort to enhance efficiency and lower stress among factory and office workers.

Japanese experiments have shown that the average number of errors per hour committed by 13 key-punch operators dropped 21 percent when their air smelled of lavender, which reduces stress; 33 percent when the air was laced with jasmine, which induces relaxation, and 54 percent when the stimulating smell of lemon was present.

This kind of Muzak-for-the-nose hasn’t caught on in North America yet, but that doesn’t mean smell is being ignored–not by a long shot. It’s one of the hottest areas of research, as typified by an infamous picture in a recent National Geographic of women sniffing men’s underarms in the name of science.

The sense of smell is still not perfectly understood. We do know that air drawn into the nose passes over an area called the olfactory epithelium, which is about four or five square centimetres in size and covered by mucus. (By comparison, dogs have 18 square centimetres of olfactory epithelium, and cats have 21 square centimetres.)

Molecules from “smelly” substances must penetrate the mucus in order to reach the sensitive cells beneath. These cells–about 10 million of them–are equipped with hair-like protuberances called cilia, which are studded with proteins. When smelly molecules interact with these proteins, they cause the cell to “fire,” sending a message down the olfactory nerves to the brain.

The receptor cells respond to a smell very quickly, but they also adapt quickly–so quickly that half the intensity is lost within a second–which helps explain why people who work in odorous environments such as certain areas of grain elevators (speaking from personal experience) can become accustomed to smells they originally found unpleasant. (Which is not to say that they don’t appreciate fresh air when they can get it!)

Sensitivity to smell varies from person to person. For example, the minimum level of hydrogen sulphide (rotten egg smell, as any former chemistry student or oilfield worker knows) that can be detected varies by a factor of 45 among people. And smelly substances themselves vary widely in smelliness: ethyl mercaptan (which smells like skunk) can be detected with only 0.00000066 milligrams per litre of air, while carbon tetrachloride (dry-cleaning fluid) can’t be detected until there are 4.5 milligrams per litre of air.

Though not up to feline or canine standards, our sense of smell is actually quite acute. And we use it more than we may realize. It, along with taste and texture, is intimately involved in our perception of the “flavour” of food. (Try eating with your nose plugged sometime!)

Scent warns us of smoke, spoiled food and other dangers. It may even provide us with information about our fellow human beings–beyond their level of personal hygiene, that is. Research is being conducted to determine if there are human “pheromones,” odorous substances that operate at a level where we can’t consciously sense them, but which influence how we relate to one another. Wolves, for example, employ pheromones as territory markers; dogs produce them as sexual attractants.

It would seem odd if almost all other mammals have pheromones and we don’t, but the jury is still out. If they do exist, and we use them in the same way many animals do, then you can expect to see Chanel Pheromone No. 5 on the shelves, because sexual attractiveness is already something we attempt to achieve through scents–although it would be ironic if the truly “attractive” pheromones are being lost beneath the perfumes and deodorants we don to make sure we don’t smell like animals.

Pheromones aside, smell has a powerful ability to communicate. The scent of fresh-baked bread may take you back to your mother’s kitchen. A particular aftershave may make you think of your father, or the smell of wet wool may remind you of mittens drying on the radiator when you were five.

The ability of smell to evoke memory is so powerful it may someday be used systematically to help people remember specific things. For example, suppose someone were murdered in a Limburger cheese factory. The witness might recall the incident better if the prevalent aroma of the murder scene was recreated in the courtroom. (Of course, everyone else might have to leave during the testimony . . .)

That use of smell hasn’t come about yet, but there are plenty of other uses for it, which is why there are companies that exist to recreate smells–a process which involves drawing the odor onto an absorbent material with an air pump, separating its components, and then analyzing them. That “sun-dried” odor some laundry detergents boast was created in just that fashion.

So the next time you’re asked to list the five senses, give your nose a break and put smell at the top of the list. It makes your food taste better, improves your memory, helps keep you alive, may influence your sex life, provides employment for hundreds of people–and, if the Japanese have their way, may soon be making you a happier, more efficient worker.

And why did I choose to write about it?

Because I smelled a story, of course.

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