friday, november 5, 1999
The nose really knows: Nostrils smell differently
By Allan Sison
Medical Tribune News Service
Ever wonder why we have two nostrils? It seems that each nostril detects scents differently, and the presence of two nostrils enhances our ability to smell and to differentiate smells, according to a recent study.
Researchers at Stanford University in Stanford, Calif, noted that air flows into the nostrils at different speeds because of the presence of a slight swelling (turbinate swelling) in one nostril. The difference in airflow causes individual nostrils to detect odors at different levels, resulting in a difference in the way the brain processes these smells.
Certain odors, known as lowsoption odorants, are smelled better when there is a reduced air flow, while high-sorption odorants, are picked up better when the air flow is increased.
Researchers from neuroscience, psychology, and psychiatry and behaviolial science had 20 people sniff a mixture of equal amounts of low-sorption and high-sorption odorants. One nostril was left open and the other was partially blocked.
The scientists found that 17. of the 20 subjects thought the mixture contained more of the low-sorption odorant (octane) when they used their partially blocked nostril. The subjects detected more of the highsorption odorant (L-carvone) when they sniffed with their open nostril. The study can be found in Thursday's issue of Nature.
In order to prove that the results were based on nostril air flow and not on which physical nostril right or left was used, the researchers repeated the experiment on eight subjects.