The Infinite Mind: Sense of Smell


Broadcast week starting: April 30, 2003

You're visiting a friend for dinner. How does the simple act of sniffing the air tell you if you'll be having curry for dinner... or lasagna? This show explores the sophisticated chemical sensing system we know as sense of smell. Dr. Stuart Firestein, Professor of Biology at Columbia University, describes new breakthroughs in our understanding of how we recognize smells. Dr. Sophia Grojsman, of International Flavors and Fragrances, talks about the blend of artistry and chemistry that she brings to her work as a perfume creator. Aromatherapist Trigve Harris, owner of New York's essential oils store Enfleurage, recommends essential oils to comfort the grief-stricken and soothe the frazzled. Joseph "Jofish" Kaye, of the Media Lab at the Massachusetts Institute of Technology, explores new uses of scent to convey abstract information. Dr. Sarah Rachel Herz, Assistant Professor of Psychology at Brown University, shares her findings on the emotional link between sense of smell and memory. And anthropologist Dr. David Howes, of Montreal's Concordia University, offers insight into olfactory codes the world over.

The show begins with an introductory essay by host Dr. Fred Goodwin. Walking his dogs, he has often observed the canine reliance on pheromones -- chemical signals that members of a species use to communicate among themselves. Scientists have long debated the existence and function of human pheromones. Recent studies in Sweden and the United States, authored by Dr. Ivanka Savic and Dr. Martha McClintock respectively, offer further evidence that humans react to exposure to male and female hormones, and that this exposure can affect mood, sexual drive, aggression, and other behaviors. Dr. McClintock's research shows that even when whatever scent associated with the hormones was masked, the hormones still produced an effect on research subjects -- elevating the moods of female volunteers and aggravating the moods of male volunteers.

Next we hear from Dr. Sophia Grojsman, a chemist who creates perfumes at International Flavors and Fragrances. She has created some of the world's best-loved and best-selling perfumes, including Yves St. Laurent's 'Paris' and Lancome's 'Tresor.' "You have to have imagination and passion to be a perfumer," says Dr. Grojsman. She compares the creation of a perfume to the composition of a symphony. "You have chords. You have crescendos. It's done in a different way but it's the same thing."

To contact Dr. Sophia Grojsman, write to her at International Flavors and Fragrances, 521 West 57th Street New York, NY 10019. Or visit the web site for International Flavors and Fragrances.

Dr. Goodwin's first interview subject is neurobiologist Dr. Stuart Firestein of Columbia University. Most odors we smell are volatile, e.g. airborne, rather than water-soluble, which is why land animals have developed a better sense of smell than fish. Odors are molecules with carbon "backbones" to which other molecules, like oxygen and hydrogen, adhere. When we sniff, we inhale odor molecules, which then bind to receptors in the nose. There are at least 3,000 molecules that we can distinguish and we have about 1,000 odor receptors in our noses. Different types of odor molecules activate different combinations of receptors, alerting us to what we are smelling. We can distinguish between odors that differ by a single molecule, or between left-handed and right-handed versions -- called "stereoisomers" -- of the same molecule. For instance, a "left-handed" version of the chemical carvone smells like spearmint and a "right-handed" version smells like caraway. Human beings demonstrate a wide variety of ability to smell. There are some odors that can be smelled by some people and not by others, and the inability to smell an odor seems to be genetic. Dr. Firestein says that scientists do not have a satisfactory way to classify smells scientifically. There's no olfactory equivalent to a color wheel. Smells are popularly classified according to their hedonic qualities, in other words, "good" smells versus "bad" smells. Some odors, for instance, sulpher-based compounds produced in rotting animals and vegetables, seem to be widely disliked but it's not known whether this dislike is hard-wired or learned. To a degree, perception of an unwholesome smell can be imaginary, as a professor of psychology famously proved when he introduced his students to a chemical that, while it couldn't be detected by some people, was found repulsive by those who could smell it. Explaining he was conducting an experiment in diffusion and olfaction, he opened a container of the chemical and set it on his desk. Soon students in the first and second rows began to wrinkle up their noses and gag. "And, as you've probably already guessed," concludes Dr. Firestein, "the substance was water."

To contact Dr. Stuart Firestein, write to him at Columbia University Biological Science, 920 Fairchild Center, MC 2438, New York, NY 10027 Click here to learn more about Dr. Firestein.

Next, The Infinite Mind's Emily Fisher interviews Trigve Harris, owner of 'Enflourage,' an aromatherapy store in New York. As an aromatherapist, Ms. Harris recommends the inhalation essential oils to promote relaxation, alleviation of pain, and sense of well being. She blends oils to achieve a synergistic effect. In the weeks following terrorist attacks in New York, Ms. Harris has been recommending white rose oil to assuage grief and heart ache, and lavender to promote relaxation. She also suggests essential oils that help to ground people, for instance woody and rooty oils like sandalwood, vetiver, and frankincense. "People need to slow down right now," she says, "and go inward, even just for a few minutes."

To contact Ms. Trigve Harris write to her at Enflourage, 321 Bleecker St, New York City, NY 10014. Tel: 212-691-1610. Or visit the web site for Ms. Harris's essential oils store, Enflourage.

How big a role does culture play in defining our associations with particular smells? Dr. David Howes is the co-author, with Constance Classen and Anthony Synott, of Aroma, the Cultural History of Smell, published by Routledge Press. He points out that there is a remarkable variety of response to smells around the world. For example, members of a pastoral group in Ethiopia find anything bovine smelling delightful, and will anoint themselves with milk and even cow dung to give themselves "the smell of wealth." Our own Western culture tends to rely on visual and auditory cues to communicate information and status, and to associate sense of smell with dogs and other "lower" animals. In the past however, as in many other cultures today, some odors connoted spirituality. For instance, the smell of roses was called "the odor of sanctity." Dr. Howes points to the recent rise of aromatherapy in the West as motivated by desire to use natural substances rather than chemicals, and to stimulate our neglected sense of smell.

To contact Dr. David Howes, write him at the Department of Sociology and Anthropology, Concordia University, 1455 de Maisonneuve boulevard, West Montréal, Québec Canada H3G 1M8 To e-mail Dr. Howes, or learn more about him, visit his web site.

Click here to order Aroma: The Cultural History of Smell, by Constance Classen, David Howes, and Anthony Synott.

Next Dr. Goodwin interviews Dr. Rachel Sarah Herz, Assistant Professor of Psychology at Brown University. Dr. Herz researches the connection between sense of smell and memory. The olfactory nerve synapses almost directly into the amygdala, in the limbic system, which is associated with memory and emotion. In researching the Proustian phenomenon of smell-triggered memory, Dr. Herz started off with the popular claim that odor is the best cue to memory. Her research indicates that memories triggered by smells are not more content specific than memories triggered by other sensory stimuli, but that they are more emotionally laden. "Odors have no meaning prior to our experience with them," says Dr. Herz. One's experience with an odor gives it meaning. For instance, if one eats something that later makes one sick, one will dislike the smell of that item (pepperoni pizza, anyone? retsina?). One might like the smell of something if it's associated with a pleasant event, even if it's an odor like the smell of skunk, which is widely considered unpleasant. The connection between olfaction, emotion and the limbic system suggests to Dr. Herz that people who lose their sense of smell may become depressed because their limbic systems have become under-used or even atrophied.

To reach Dr. Rachel Sarah Herz, write to Department of Psychology, Box 1853, Providence, Rhode Island 02912. To learn more about her work or to e-mail Dr. Herz, visit her web site.

Imagine a world in which the smell of mint indicates your stock portfolio has gained in value, or your computer gives you scent-coded reminders of upcoming meetings. According to Joseph "Jofish" Kaye, a researcher at the Media Lab of the Massachusetts Institute of Technology, that world may not be far off. In commentary that concludes the show, Joseph "Jofish" Kaye tells of his work in using computer-generated smell to communicate abstract information. "If that sounds a little 'far out' to you," says Mr. Kaye, "consider the rise of the sound card and the MP3. Users first started relying on sound in computers for entertainment - games, basically. But once the ball got rolling, a computer without sound seemed like it was missing something." He tells us of projects he developed at MIT to explore symbolic olfactory display, including 'In Stync' and 'Honey, I'm Home.'

To contact Joseph "Jofish" Kaye, write to him at 15 Lee St, Somerville MA 02145 or visit his web site.

-- Emily Fisher, producer

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