Two sides to it


By Alison Motluk in Miami Beach YOUR two nostrils can’t agree on what they smell. Researchers in California say their different perceptions may give the brain a richer picture of what’s out there. At any one time, air flows through one nostril more quickly than it does through the other because of a slight swelling in one side of the nose. Every few hours, the swelling moves from one nostril to the other. This affects how quickly a scent is drawn into each. Also, different scents are absorbed through the nose’s mucous membrane at different rates. Noam Sobel and his colleagues at Stanford University thought these two factors might create a different smell profile from each nostril. Substances that are absorbed slowly might smell stronger if sniffed through the low-airflow nostril, where they have more time to be absorbed, while quickly absorbed smells might be easier to detect in the high-airflow nostril. The team asked 20 volunteers to sniff a substance made up of equal parts of octane and L-carvone. Octane is absorbed slowly and L-carvone quickly. The volunteers rated the proportions they detected through one nostril at a time. The researchers also measured the rate of airflow through each nostril. As expected, they found that for 17 of the volunteers, sniffing through the high-airflow nostril gave the impression of more L-carvone whereas the low-airflow nostril signalled more octane. “Each nostril perceives the world differently,” Sobel told the meeting. “The brain is receiving two disparate images of the olfactory world.” This may improve the nose’s accuracy by increasing the number of smells detected in a single sniff. More on these topics:
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