Never Mind Eyesight, Your Nose Knows Much More

5

The human eye can distinguish more than 2 million distinct colors. But scientists studying smell now say they have their vision colleagues beat: The human nose, they say, can distinguish more than a trillion different smells.

Yes, trillion with a T.

That new figure displaces a much more modest estimate. Until now, smell researchers have been saying the human nose can distinguish about 10,000 smells.

But Andreas Keller at The Rockefeller University says that number comes from a discredited idea from the early 20th century, which asserted that there are four primary smells, the way there are primary colors. That's just plain wrong.

"And I found that so interesting and ridiculous that I thought it would be time to do an experiment and test how many odors there really are," Keller says.

So he and his colleagues at The Rockefeller University and the Howard Hughes Medical Instituteput together an experiment. They started with 128 chemicals with distinct smells, and started mixing them together —as many as 30 chemicals per bottle.

"Subjects come in and they're given three little bottles with odors in them," Keller explains. Two of the bottles are identical. The third is slightly different. "And the task is simply to tell which one is different."

Through this process, the scientists found that the human nose could do a remarkable job of distinguishing very small differences between smells. Once they figured out the percentage of these mixtures a person could distinguish, they called in a mathematician, who figured out how many possible unique odors you can make from elaborate mixtures of these 128 chemicals.

"And that's how the number of 1 trillion came about," Keller says.

It's true that a human being would never encounter a trillion different smells in a lifetime. "And most of the smells we tested in our test were probably never smelled by a human being before," Keller says.

But the human nose has presumably evolved to be able to detect tiny differences among smells — say to tell the difference between fresh food and something that's just beginning to spoil. That could be a matter of life and death.

So why do this experiment?

Written By: Richard Harris
continue to source article at npr.org

5 COMMENTS

  1. Sugar refineries in the UK often used process condensate as boiler feed water. In order to ensure there was no build up of sugar in the feed water they trained operators in steam raising plant to ‘sniff for sugar’. Detection to a few parts per million were claimed. The development of the alpha-napthol test which gave a quick and reliable visual indication of sugar traces replaced the practice. Probably because it eliminated the subjectivity having to rely on the senses and judgement of one operator and brought the testing and logging within laboratory and quality assurance procedures.

  2. When ever I smell tarmac I experience a distinct childhood memory.

    When I smell disinfectant I recall being in hospital aged about ten; that is certainly not an odour experienced today in those establishments.

    Kick the meddling politicians and privately employed managers and “cleaners” out of our precious National Health Service hospitals and, BRING BACK MATRON!

    She’ll kick arse.

  3. Scents are definitely linked strongly to memory – where a visual scene is recreated involuntarily of the last time you smelled that particular smell… it often seems to be an emotional response as some smells are linked to repulsive reactions too….the smell of fresh roasted nuts or baked bread sends us all following our noses…. if we are hungry…
    Even though smells are subjective to where we all live….we recognise a lot of common smells and their associated response mechanisms…like fire and sea shores

    • I have read (and experienced) the idea that Deja vu is triggered (often) by smells. It is very interesting to me. You walk down a hallway every day for 18 years (I am talking about where i work) and never get deja vu. However, that one day, you are walking down the same damn hallway and the foods class is cooking apple pie and suddenly you are in that stuporous suspended animation of deja vu. I think it occurs most strongly when multiple senses have the same memory.

      So, in my apple pie example, your eyes are seeing the same repetitive visual stimuli and you are having “eye memory”, then the apple pie smell hits and you are having “nose memory”, and then a sound comes over the school loudspeaker and you are having “ear memory”. When all these memories hit your consciousness simultaneously, BAM…. Deja vu!!!

      In reply to #3 by Light Wave:

      Scents are definitely linked strongly to memory – where a visual scene is recreated involuntarily of the last time you smelled that particular smell… it often seems to be an emotional response as some smells are linked to repulsive reactions too….the smell of fresh roasted nuts or baked bread se…

Leave a Reply