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| The strange science behind our sense of smell | The strange science behind our sense of smell |
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| People make decisions every day based on smell. We choose soaps, perfumes and candles with scents we prefer and use cleaning products that make our homes smell good. If food smells rotten, humans avoid it because our noses signal our bodies that it will make us sick. | People make decisions every day based on smell. We choose soaps, perfumes and candles with scents we prefer and use cleaning products that make our homes smell good. If food smells rotten, humans avoid it because our noses signal our bodies that it will make us sick. |
| But traditionally, researchers have understood little about how our nose specifically works; in the past few decades, however, scientists have made strides in understanding how this clever organ operates, and keeps us safe. | But traditionally, researchers have understood little about how our nose specifically works; in the past few decades, however, scientists have made strides in understanding how this clever organ operates, and keeps us safe. |
| How we smell | How we smell |
| Scientists say we smell when we suck up air into our nostrils and over millions of olfactory receptor neurons. Odor molecules in the air stimulate and inhibit the receptors, writes Cory Binns in Live Science. Each aroma sets off the signal made by the receptors, travels along the olfactory nerve to the olfactory bulb, (sitting right underneath the front the brain). Signals from that bulb are what tell your brain what smells. | Scientists say we smell when we suck up air into our nostrils and over millions of olfactory receptor neurons. Odor molecules in the air stimulate and inhibit the receptors, writes Cory Binns in Live Science. Each aroma sets off the signal made by the receptors, travels along the olfactory nerve to the olfactory bulb, (sitting right underneath the front the brain). Signals from that bulb are what tell your brain what smells. |
| Most scents contain hundreds of different odor molecules. And humans, along with mice, have 1,000 smell receptors in their noses, according to Dr Linda Buck at the Fred Hutchinson Cancer Research Center. In 1999, Buck found with her team that altering the structure of an odorant also means its smell can profoundly change – a shift in concentration can turn a scent from pleasant to disgusting. Octanol, for example, found in petroleum and natural gas, exudes orange and rose-like smells. Change one atom and the odor becomes octanoic acid, a rancid, sweaty smell. Meanwhile, Indole, found in both coal tar and perfumes, stinks when concentrated yet smells like jasmine when sufficiently diluted. | |
| In 1995, biophysicist Dr Luca Turin of Greece’s Fleming Biomedical Research Sciences Center cultivated a new (and controversial) theory of smell challenging the idea that smell depends on the shapes of molecules and the molecules’ vibrations. In a 1996 paper in Chemical Senses, Turin said we can view molecules as a collection of atoms on springs. Energy of the right frequency can cause the springs to vibrate, and these vibrations explain smell. | |
| The amazing power of the nose | The amazing power of the nose |
| Our sense of smell trumps all other senses. In The Emperor of Scent: A True Story of Perfume and Obsession, author Chandler Burr, writes that taste is a dwarfish, minimally functional sense responding to only six different stimuli: sweet, sour, salt, bitter, richness and astringent. Smell, on the other hand, gives us 90% of what we taste, which explains why we taste less when we’re congested. | Our sense of smell trumps all other senses. In The Emperor of Scent: A True Story of Perfume and Obsession, author Chandler Burr, writes that taste is a dwarfish, minimally functional sense responding to only six different stimuli: sweet, sour, salt, bitter, richness and astringent. Smell, on the other hand, gives us 90% of what we taste, which explains why we taste less when we’re congested. |
| Our sense of smell is also highly specific, and accurate, not unlike the spectroscope, a scientific instrument, which can faultlessly identify atoms inside and the molecules they make up by measuring molecular vibrations. Burr writes in 1938, English scientist Malcolm Dyson noticed a specific, amazing power of the human nose: we can smell and instantly identify the actual actions hidden inside a molecule. One sniff tells us for instance, “nitrogen atoms in here”, “sulfur atoms in here”, and we never get it wrong. Our sense of smell never misanalyses atoms – we can tell every molecule apart from every other. | |
| Lay and scientific research (from 1927) states the nose responds to 10,000+ distinguishable molecular smells. However, researchers often questioned the small figure and lack of data. In 2014, research by Leslie Vosshall and Andreas Keller, researchers at the Rockefeller University in New York, found the human nose can distinguish at least 1 trillion different odors, making the nose far more sensitive than any other human organ in terms of the different stimuli it can discriminate. | Lay and scientific research (from 1927) states the nose responds to 10,000+ distinguishable molecular smells. However, researchers often questioned the small figure and lack of data. In 2014, research by Leslie Vosshall and Andreas Keller, researchers at the Rockefeller University in New York, found the human nose can distinguish at least 1 trillion different odors, making the nose far more sensitive than any other human organ in terms of the different stimuli it can discriminate. |
| Heightened smells | Heightened smells |
| Smell also keeps us safe. A study in 2000 by Drs Richard Blum and LeRoy Heinrichs at Stanford University’s School of Medicine, found our sense of smell triggers nausea in humans, and pregnant women experience a heightened sense of smell during morning sickness. Volatile smells, such as coffee, petroleum, and meat all trigger nausea in pregnant women, the researchers write. Other research links the heightened sense of smell a woman experiences during morning sickness to medieval times, before refrigeration, when smell protected a woman (and her fetus) from eating food that was not clean or putrid. In this case, smell may protect a woman from potential miscarriage. | |
| Each individual also has a unique set of genetic variations that cause humans to smell things differently, according to Andreas Keller and other researchers published in Nature Neuroscience. Keller also researched several hundred subjects from the New York area, rating their like and dislike of 60+ different odors. The subjects favored vanillin the most and Isovaleric acid, which gives smelly cheese its pungent odor, the least. Overall, he finds fruit is universally a pleasant odor vs. decaying flesh, naturally, an unpleasant one. | |
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