We’ve long known that a human’s sense of smell triggers the strongest memories. But recently, scientists figured out exactly how impressive our nostrils really are. According to researchers, the human nose can distinguish at least one trillion different odors, which is millions more than previously estimated.
The findings, published in Science Magazine, debunk the widely-accepted figure that humans can only detect 10,000 scents, putting the sense of smell well below the capabilities of hearing and sight. This number dated back to the 1920s and was not supported by data.
Scientists have estimated that the human ear can distinguish between 340,000 sounds, and the eye and its mere three receptors can differentiate between several million colors. The nose’s abilities, meanwhile, are carried out with the help of 400 olfactory receptors – it’s the largest gene family in the human genome. It makes sense that we would be able to discern many more smells – everything from roses to bad breath - than we can colors.
“Our analysis shows that the human capacity for discriminating smells is much larger than anyone anticipated,” study co-author Leslie Vosshall, head of Rockefeller University’s Laboratory of Neurogenetics and Behavior, said in the report. “For smell, nobody ever took the time to test.”
In the study, 26 volunteers were instructed to distinguish between odor mixtures made with 128 different odorant molecules that came from common flavor and fragrance ingredients such as vanilla, mint, apple as well as less pleasant aromas. However, these were combined in groups of up to 30, creating a sort of olfactory white noise.
“When we started mixing them together, we mixed them at equal intensity so all the smells were diluted to the same intensity,” lead author Dr. Andreas Keller from Rockefeller University explained to ABC News.
Participants sampled three vials of scents at a time, two of which were identical, the other having different smell. The test was to see if they could discern which was the outlier, completing 264 comparisons.
While volunteers’ abilities varied greatly, they could, on average, tell the difference between vials with up to 51 percent of the same components. Researchers then extrapolated how many odors the average person could smell if all possible combinations of the 128 odors were sampled, coming to their estimate of at least one trillion.