Prior to today, the official scientific answer to the question, "How many scents can the human nose detect?" was a measly 10,000. But now, thanks to a new study in Science, the answer is 1 trillion, give or take. Researchers had long assumed that the first number, based on relatively rudimentary tests in the 1920s, was way off the mark, and the new study is the first significant one to apply modern methods to revise it, reports Nature. The 1 trillion figure is seen as an average, with some people able to detect as "few" as 80 million odors and others able to pick up on a mind-boggling "thousand trillion" of them, according to the scientists' extrapolations. “Ten thousand is kind of pathetic—it’s a pretty low number,” says molecular neurobiologist Leslie Voshall of the Rockefeller University, a co-author of the study. “It led to the idea that humans have a comparatively low sense of smell.”
For their experiment, the scientists used "a procedure similar to a hearing exam, in which listeners must try to distinguish between two tones," explains the Washington Post. Researchers combined 128 different odor molecules to create composite scents of varying complexity, then ran them by 26 test subjects. Participants got three vials—two had identical odors and the third was slightly different—and had to pick the odd one out, reports NPR. The analysis gets more complicated than that, but after hundreds of experiments on each subject, researchers extrapolated the results to arrive at the 1 trillion average. The study is being well received in the field. “Their work confirms that smell is an incredibly rich, variable, and nuanced medium,” says one olfactory scientist not involved with the research. “It’s why you can dive so deeply into the aroma of a wine, when there are only a few ounces in the glass." (More discoveries stories.)
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