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    Your Sense of Smell May Be Keener Than Thought

    Study suggests people can detect more than a trillion distinct odors


    The researchers said the human ability to smell was so strong that some of the participants were able to tell odors apart even when the vials shared as much as 90 percent of the same smell building blocks and were therefore nearly -- but not quite -- identical.

    Test results were then funneled into a complex mathematical formula. The result: the calculation that the human nose is capable of distinguishing a minimum of 1 trillion different smells.

    Despite the finding that human smell is actually a very powerful sensory instrument, Keller acknowledged that, if forced to make a choice between giving up the sense of hearing, sight or smell, he would give up smell.

    "I would disagree that smell is less 'evolved' than these other senses," he said. "Smell just evolved for other purposes -- discriminating [between] very similar smells -- than the other senses."

    "However, all that olfaction tells us about the world is what different smells there are," Keller said. "In contrast, vision tells us mainly about the spatial structure of our environment. Color-blind vision is still very useful. Odor-blind olfaction is no olfaction at all."

    Joel Mainland, an assistant member of the Monell Chemical Senses Center in Philadelphia, said the study findings might still underplay the true strength of human smell.

    "The fact is, we are much better at olfaction than we think we are," Mainland said. "First of all, humans have 400 types of smell receptors, compared with just four in color vision and probably around 40 with respect to taste. With a smell alphabet comprised of 400 receptors, the amount of odors you can get is incredible."

    "This is a difficult experiment to conceive," he said. "They've actually simplified things a lot, which is to say that while coffee, for example, has about 400 odor components in it, they used mixtures with only 30 at most. They also matched all the components for intensity, which never really happens in a natural product or even in a perfume. There's typically a huge range of intensity."

    "If you were to do a test involving all kinds of intensities and many more components, you'd arrive at a figure that is probably much, much higher than a trillion," Mainland said. "I'd say that a trillion is probably a severe underestimate of our ability to smell. Our sense of smell is really, really underappreciated."

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