The human nose can detect a large number of odors.
New research shows that our noses can actually detect up to 1 trillion odors. The latest findings far outweigh the commonly reported guess of 10,000 smells.
Although boundaries and limitations of the visual and auditory systems are known, this study was the first to discover the limitations of the human nose.
Scientists from the Rockefeller University began by testing the proboscis, or the nose of a mammal, with scent mixtures containing 128 various smell molecules. Researchers then asked participants to choose from among the three scents, including two of the same scent and one scent that was a bit different.
The study indicated that more than half of the participants were able to find the odd smell, providing that the mixture was at least 50 percent different than the others. The scientists then looked at their own data to determine the every possible smell combination a human nose can distinguish, leading them to their final figure of 1 trillion.
Andreas Keller, study lead, explained to Science that, “It’s not that we need to smell all those odors, but what happened is that our olfactory system evolved to have a very good resolution to discriminate very similar smells.”
The study is expected to dispel the commonly quoted estimate of 10,000 smells, a figure that many researchers found difficult to believe.
Leslie Vosshall, study author and molecular neurobiologist at the Rockefeller University, stated, “Ten thousand is kind of pathetic – it’s a pretty low number.” She continued, “It led to the idea that humans have a comparatively low sense of smell.”
Vosshall and fellow researchers tested a total of 26 noses, relying on a procedure similar to a hearing exam, where participants try to distinguish between two tones. Each participant was given three vials, two with the same scent and one that was different.
After completion of hundreds of tests on every subject, the researchers believed that the subjects’ performance would be similar in distinguishing all of the possible smells made in the lab.