Synopsis: The sense of smell evokes powerful memories and makes food taste good, but it also has important functions in interpersonal relations and personal safety. Experts discuss the science behind it.

Host: Nancy Benson. Guests: Dr. Charles Wysocki, Behavioral Neuroscientist Emeritus, Monell Chemical Senses Center; Neil Pasricha, author, The Book of Awesome

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Nancy Benson: Nothing says spring like the first open window after a long winter, or the smell of newly cut grass — so invigorating! However, for millions of people with seasonal allergies, these simple pleasures don’t exist because their noses are congested. And not only can allergy sufferers not smell, they usually can’t taste much either. About 75 percent of what we taste actually comes from the sense of smell.

Charles Wysocki: What we experience as aroma comes from the nose. It’s molecules of what we are ingesting that go to the upper regions in the nose. Bridge of the nose between the eyes basically is where the smell receptors are located and there are millions of those. And those molecules have to interact with specific proteins on the sensory cells for there to be an experience of smell.

Benson: That’s Dr. Charles Wysocki, Behavioral Neuroscientist Emeritus with Monell Chemical Senses Center in Philadelphia.

Wysocki: If those molecules cannot reach those receptor cells, for example, if an individual is having an allergic attack and it’s severe enough then it may result in congestion. Congestion blocks the flow of air to the sensory cells in the nose, and hence an individual may have a reduced perception or an absent perception of the smells that are associated with what they’re eating or they’re drinking.

Benson: If you want to experience just how important these sensory cells in the nose are to taste, try this experiment.

Wysocki: Take three different flavored jelly beans and put them in one hand and mix them around, close your eyes, and with your other hand plug your nose with your forefinger and you thumb. Pop one of those jellybeans into your mouth, chew it. You’ll experience a texture you’ll also experience the sweetness of the jellybean and then swallow. Once you’ve completed the swallow, let go of your nose and voila now and only after letting go of your nose, now you can correctly label the flavor of the jellybean that you put into your mouth.

Benson: Of course, our sense of smell has far more significance than just making our food taste better. It also helps keep us safe.

Wysocki: Smell is important as a warning signal, for example the natural gas companies put warning smells inside the gas so that if you smell it, you know enough to either evacuate or importantly call someone for help. The same might be true if you’re going into the refrigerator and pull out some leftovers and you can’t smell very well or you can’t smell at all because of an allergy attack you may be ingesting something that is spoiled and it may poison you.

Benson: And when it comes to our own bodily odors, which admittedly can be quite noxious, our sense of smell has social ramifications. For example, we’ve all been stuck on a plane or bus sitting next to someone who stinks to high heaven. You gag and try to be polite, but can’t wait to get away. Next time, pop a mint in your mouth and you won’t be so strongly affected. But the opposite is also true, though a lot more subtle. So much so we may not even be aware it’s happening.

Wysocki: But it’s more difficult to come up with situations where you say, well, I like being with this person because I like how he or she smells. Having said that, it is a lot easier for women to do that then it is for men. Women pay very close attention to human body odor. Men are more visual creatures. And when I say body odor what I mean is that each individual has a unique body odor that is regulated in part by a set of genes that regulates the immune system.

Benson: All of this nasal communication is completely unconscious, and pretty much out of our control. Researchers haven’t yet identified the complex chemicals in human male underarm odor, but they do know these compounds affect the endocrine system regulating women’s menstrual cycle. And yet another set of complex compounds affects the behavior of a newborn infant.

Wysocki: The body odor taken from around the nipples of a lactating mother is by itself, just the smell of it alone, is sufficient to have the baby start trying to move towards the smell so that’s called an attractive pheromone. That’s about the only attractive pheromone that has been identified even though if you go on the internet you can probably find thousands and thousands of websites that are advertising sex attracted pheromones, but there hasn’t been any good solid biomedical evidence for the existence of such in people.

Benson: Even the notion that you can smell fear has some truth to it. Certainly dogs can smell fear.

Wysocki: In about the last decade, there have been a number of laboratories who have published very convincing evidence that when an individual is stressed, anxious or startled, their body odor changes, and that body odor can be identified as different from the body odor from the same individual in a non-stressed situation or a non-fearful situation. More recently there have been numerous studies published showing that when an individual is exposed to body odor from a frightened individual or a stressed individual, their behavior changes as well. They become more vigilant, they are much more aware of their environment, and they respond more quickly to potential threats. So, yes it does appear that people are capable of smelling fear.

Benson: But why do certain smells also stir up such strong memories? Why, for example, when you smell a certain perfume you haven’t sniffed in years, your mother who died decades ago suddenly comes alive to you?

Neil Pasricha: We all have those little smells that bring us back they say the sense of smell is you know the one that kind of triggers this older primal part of our brain more than anything else.

Benson: That’s Neil Pasricha best-selling author of The Book Of Awesome.

Pasricha: And that’s the thing that smells can do, they can bring you back to the time when you were a kid, the time you were playing baseball, the time where you had like a backyard birthday party or you had a barbecue with your extended family, and it’s a beautiful thing to be alive and to sort of be reminded of these smells and your friends as someone who I think is getting a lot of pleasure out of life by remembering those little things.

Wysocki: If one takes a look at the projections from the nose to a part of the brain called the limbic system it regulates moods and emotions and a different part of the brain that encodes and decodes memories. The sense of smell is the equivalent of taking an interstate highway. Other sensory systems bring it to the same places, but it’s the equivalent of taking country roads. So the sense of smell does have very direct access to and can influence and be influenced by the limbic system and also the part of the brain that encodes and decodes memories.

Benson: Many different kinds of nasal sprays and medications can help with congestion, and with allergy season upon us, now’s the time to use them, ‘cause you sure don’t want to miss out on the smell of your steaks grilling in the back yard. You can learn more about our guests and find a link to the book of awesome by visiting our web site at radio health journal dot net. Our writer this week is Polly Hansen. Our production director is Sean Waldron. I’m Nancy Benson.

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