The human nose may distinguish more than a trillion smells
A 2014 experiment blew up the textbook claim that people can tell apart only 10,000 odors.
For decades, textbooks repeated a figure dating to the 1920s: that the human nose could distinguish about 10,000 different smells. The number had little hard evidence behind it.
In 2014, researchers led by Andreas Keller and Leslie Vosshall at Rockefeller University, working with the Howard Hughes Medical Institute, put it to the test. They mixed 128 odour molecules into random blends of 10, 20 or 30 components and asked volunteers to spot the odd one out among three vials. From how reliably people told mixtures apart, they extrapolated to the full space of possible blends.
The result, published in Science: humans can discriminate at least one trillion distinct odours — orders of magnitude beyond the old estimate.
The figure is a statistical extrapolation, not a literal count, and other scientists have argued the true number could be far higher or lower. What is not in dispute is the headline: our sense of smell is far sharper than we give it credit for.
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