Nose can detect how many smells

A team led by Dr. Andreas Keller of Rockefeller University set out to determine the resolution of the human olfactory system by testing how well humans could distinguish mixes of odors. Results were published in Science on March 21, The researchers placed 10, 20, or 30 odor components in equal ratios into vials labeled with bar codes.

The odors were taken from a collection of odorous molecules with similar intensities, so that no one odor dominated. The molecules included some responsible for scents such as orange and spearmint.

Participants were given sets of 3 vials. Two of the vials contained the same mixture, while the third contained a different one. Participants completed tests. The researchers found large variations in how many mixtures the 26 participants could distinguish. Science is an inherently error-fraught business, but mistakes like this remind us of one of the most important ground rules of the process: reproducibility.

But that only means the most fascinating discoveries are still ahead of us. You can read the original Science paper here and the new rebuttal study here. Another rebuttal paper is available in pre-print on arXiv. Contact the author at maddie. Science is an inherently error-fraught business The A. By Maddie Stone. Shop at Amazon. Over and over again, it's reported that we can only distinguish between about 10, different scents—a large number, but one that's easily dwarfed by that of dogs, estimated to have a sense of smell that's 1, to 10, times more sensitive than ours.

It may be indisputable that dogs do have a superior sense of smell, but new research suggests that our own isn't too shabby either. And it turns out that the "10, different scents" figure, concocted in the s, was a theoretical estimate, not based on any hard data.

When a group of researchers from the Rockefeller University sought to rigorously figure out for the first time how many scents we can distinguish, they showed the s figure to be a dramatic underestimate.

In a study published today in Science , they show that—at least among the 26 participants in their study—the human nose is actually capable of distinguishing between something on the order of a trillion different scents. A big part of the reason it took so long to accurately gauge our scent sensitivity is that it's much more difficult to do so than, say, test the range of wavelengths of light the human eye can perceive, or the range of soundwaves the human ear can hear.

But the researchers had a hunch that the real number was far greater than 10,, because it was previously documented that humans have upwards of different smell receptors which work in concert. For comparison, the three light receptors in the human eye allow us to see an estimated 10 million colors. Noting that the vast majority of real-world scents are the result of many molecules mixed together—the smell of a rose, for instance, is the result of unique molecules in combination—the researchers developed a method to test their hunch.