WASHINGTON - The human nose can distinguish at least one trillion different odors, millions more than previously estimated, US researchers said Thursday.
For decades, scientists accepted that humans could detect only 10,000 scents, putting the sense of smell well below the capabilities of sight and hearing.
"Our analysis shows that the human capacity for discriminating smells is much larger than anyone anticipated, said study co-author Leslie Vosshall, head of Rockefeller University's Laboratory of Neurogenetics and Behavior.
The previous estimate for the nose's capabilities -- which are carried out with the help of 400 olfactory receptors -- dated to the 1920s and was not backed by data.
Researchers have estimated that the human eye and its mere three receptors can distinguish several million colors and that the ear can discriminate 340,000sounds.
"For smell, nobody ever took the time to test," Vosshall said.
To conduct their research, scientists subjected 26 participants to mixtures made with 128 different odorant molecules that individually might evoke grass, citrus or various chemicals, but were combined in groupings of up to 30.
"We didn't want them to be explicitly recognizable, so most of our mixtures were pretty nasty and weird," Vosshall said.
"We wanted people to pay attention to 'here's this really complex thing – can I pick another complex thing as being different?'"