Heard That Humans Can Smell 10,000 Odors? Here's Why You Heard That.

If you poke around online, you’ll find someone claiming authoritatively that humans can distinguish 10,000 odors. Unfortunately, that’s not true. It’s based on an experiment from the 1920s, that tried — and failed — to quantify smell. But here’s how it became a pop fact.

In 1927, scientists Lloyd Henderson and Ernest Crocker started by breaking scents down into what they considered four major components; fragrant, acid, burnt, and caprylic. Fragrant is floral and fruity. Acid and burnt are self-explanatory. Carprylic is “animal smell.” The two even came up with chemicals that were characteristic of each smell. For example, according to Henderson and Crocker, “burnt” was characterized by the compound guaiacol, which is a compound usually present in wood smoke.

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Crocker and Henderson decided that each scent component would be rated in intensity from 0 to 8. In any given smell, each of the components would be rated on its relative intensity. A rose, the scientists decided, was a 6 fragrant, 4 acid, 2 burnt, 3 caprylic, or 6423. Every smell imaginable, then, could be assigned a four-digit number. Their system allowed for 6,561 different identifiable scents. Because they had done research on the subject of smells, they became the go-to guys to ask about scent. No one objected when Crocker rounded the 6,561 scents up to 10,000 scents a few years after their experiment.

It’s a very nice round number, and we like round numbers, which is why it has been kicking around public consciousness since the 1930s. Sensory psychologist Avery Gilbert even noted that it was cited in a press release from the Nobel Assembly. However, it’s not based on anything more than a rough estimate of a flawed system.

Top Image: Atoma.

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