The Nose Knows Left From Right

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Few of us are ever aware of it, but one nostril is always pulling in a tiny bit more air than the other, the result of minute swelling in the nasal lining that switches from one side to the other every few hours. The phenomenon has seemed to be little more than an anatomical curiosity.

But a team of researchers based in the U.S. and Israel has shown otherwise. From animal studies, the scientists knew that some odors are detected more easily when they're flowing past nasal tissue quickly, and others when they're moving slowly. So the researchers tested human subjects with a mix of two chemicals, asking them to sniff through one nostril, then the other. Sure enough, as reported in last week's issue of Nature, the sniffers thought they were smelling different mixtures when they were really just getting a different olfactory take on a single mixture.

Why did evolution create such an odd system? Perhaps, the scientists theorize, to give humans the best possible chance to pick up all the odors around them--a sort of stereo smelling that could have boosted the odds of finding food or sniffing out enemies.

--By Michael D. Lemonick