The upshot is that you can expect about 30 percent of your receptor arsenal to function differently than your neighbor’s, which explains why conversations starting with “Do you smell that?” so frequently devolve into farce. A substance like androsterone—a musk found in human sweat, truffles and elsewhere—can smell like sandalwood or urine or nothing at all, depending on the nature of the smeller. For a long time researchers believed that “asparagus pee” wasn’t universal, because only certain people reported a malodorous bouquet after consuming the spiky veggie. In fact, only some unlucky noses can detect it, but for those who can, the odor is universal—a fact those subjects realized “only when they smelled each others’ urine,” Keller says.

— Read more in Sniffing Out the Science of Smelling at Smithsonian.