How competitive is your nose?

September 25, 2009


How competitive is your nose? Did you know, and do you care, that when the nose encounters two different scents simultaneously, the brain processes them separately through each nostril in an alternating fashion? This means your nostrils are competitive and act almost as rivals in tracking down different odours. We are indebted to those find fellows at Rice University in Houston for looking at this as part of a psychology study.

They took 12 volunteers and got them to sample smells from two bottles; one contained phenyl ethyl alcohol, which smells like a rose, and the other had n-butanol, which smells like a marker pen. The bottles were fitted with nosepieces so that volunteers could sample both scents simultaneously, one through each nostril. During 20 rounds of sampling, all 12 participants experienced switches between smelling predominantly the rose scent and smelling predominantly the marker scent. In the laboratory setting in which each nostril simultaneously received a different smell, the participants experienced an ‘olfactory illusion,’ so that instead of perceiving a constant mixture of the two smells, they perceive one of the smells, followed by the other, in an alternating fashion. It is as if the nostrils were competing with one another, and although both smells are equally present, the brain attends to predominantly one of them at a time.

This sort of rivalry is not new apparently as our eyes do the same thing. When they simultaneously view two different images, one for each eye, they are seen alternately one at a time. The same goes for your hearing as when alternating tones an octave apart are played out of phase to each ear, most people experience a single tone that goes back and forth.

This research is aimed long term at contributing to the assessment and cure of olfactory disorders in patients and, in particular, the elderly.


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