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Human smell is much more sensitive than expected
The human nose can distinguish over a trillion (1,000,000,000,000) smells. This is the result of a US study by Rockefeller University in New York. This means that the nose far outperforms eyes and ears. So far, estimates have assumed that the human olfactory organ can only differentiate between around 10,000 different smells.
Nose has phenomenal capabilities The human nose can perceive significantly more smells than previously thought. This is the conclusion reached by Leslie Vosshall, smell expert at Rockefeller University, and his colleagues as part of their study: "The message is that our smell is much more sensitive than we think," said Vosshall. "We just do not pay attention to this and use it little in everyday life." The researchers write in the scientific journal "Science" that more than a trillion smells can be perceived by our noses.
In the 1920s, an investigation came to the conclusion that the human sense of smell can distinguish around 10,000 smells. "Everyone in the industry suspected this number was ridiculously small," explains Vosshall. But only his colleague Andreas Keller had checked the number in scientific tests.
Odors "are made up of many molecules and are very complex". According to the scientist, "the scent of the rose consists of 275 different components, of which only a small percentage is consciously perceived". This complexity means that researching the sense of smell is much more difficult than examining sight or hearing. Compared to the nose, eyes and ears perceive much less. Estimates assume that the eye can see between 2.3 million and 7.5 million colors and the ear can register around 340,000 audible tones.
Today, the sense of smell plays a subordinate role in everyday life. For their study, the researchers gave the test subjects three ampoules with fragrance mixtures. Two were identical, one differed in a few fragrance components. "Our trick was to use a mixture of odor molecules and we use the overlap ratio of two mixtures to measure the sensitivity of the sense of smell," reports Andreas Keller. During the tests, the study participants were asked to find out the sample whose smell differed slightly from the others. The test was repeated 264 times with each subject to achieve representative results. An extrapolation finally showed that "the human nose can distinguish around 1,000,000,000,000 smells".
The researchers suspect that the relatively small importance of the sense of smell today could be related to walking upright. Because the primitive man was much closer to the ground with his nose stooped, the source of most smells. Added to this are the habits and amenities of the modern world, through which many smells no longer arise, because they are prevented in advance, for example by refrigerators and daily showering. "This could explain our attitude that the smell - compared to hearing and seeing - is insignificant," explained Keller. The results of the study are a step towards researching the difficult to grasp quantity of the sense of smell, so the way would pave the way for more in-depth investigations, says the scientist. (ag)