A new story in the Washington Post’s Health, Science & Environment section, entitled Human nose can detect at least 1 trillion odors — far more than thought, says study of smell, appears to upend conventional wisdom about the number of smells that humans can identify. The general number has been around 10,000 as long as I can remember. By contrast, we can see “a few million different colors” and our ears can take in around 340,000 different tones. So while smell used to be a lot farther down on the sensory spectrum, this study would appear to rocket our sense of smell to the front of the line. For beer lovers, that can’t be a surprise, because our nose conveys so much more about a beer than seeing or hearing it can, and not even tasting it comes close, as any person who’s had a head cold can tell you, after trying to taste a beer without a working sense of smell.
The study itself, Humans Can Discriminate More than 1 Trillion Olfactory Stimuli, will be published in the journal Science. Here’s the abstract:
Humans can discriminate several million different colors and almost half a million different tones, but the number of discriminable olfactory stimuli remains unknown. The lay and scientific literature typically claims that humans can discriminate 10,000 odors, but this number has never been empirically validated. We determined the resolution of the human sense of smell by testing the capacity of humans to discriminate odor mixtures with varying numbers of shared components. On the basis of the results of psychophysical testing, we calculated that humans can discriminate at least 1 trillion olfactory stimuli. This is far more than previous estimates of distinguishable olfactory stimuli. It demonstrates that the human olfactory system, with its hundreds of different olfactory receptors, far outperforms the other senses in the number of physically different stimuli it can discriminate.
It will be very interesting to see if further studies corroborate this finding, but frankly it makes a lot of sense (no pun intended).
Science also has a short interview with Andreas Keller, one of the scientists who worked on the study, where he explains some of the reasons his team thinks that their study has shown we’re capable of so many more aromas than previously thought.