Do You Smell That Smell?

by Elizabeth Norton Lasley

January, 2007

Homo sapiens isn’t best known for the ability to track a scent, but new research shows that humans may “smell” better than previously thought.

In a study reported in the January Nature Neuroscience, students at the University of California at Berkeley were asked to sniff out the path of a chocolate-drenched rope through a grassy field. On all fours, noses to the ground, the volunteers wore blindfolds, earplugs, and padded clothing to block other sensory input. Most found the scent trail successfully, developing a zigzag pattern as dogs do. With practice, they completed the challenge more quickly, with fewer zigzags.

“The human sense of smell is quite good,” says lead author Jess Porter, a biophysicist at Berkeley. “Our purpose in this study was to test whether the two nostrils work independently.”

In a second phase, participants with one nostril taped shut took longer to find the trail. “This might have resulted from working with only half as much information,” Porter says. So she and her colleagues devised a nose plug with one intake hole that diverged into two conduits, one into each nostril. Subjects still had the same amount of air, but their nostrils had gone from stereo to mono, so to speak. In this phase, too, they took longer to follow the scent.

The finding suggests that nostrils, like eyes and ears, draw on information from two different directions at once. Porter notes that frequent sniffing improves tracking time—dogs sniff up to six times per second—and that people can improve their sense of smell with patience and practice.