Humans Show Keen Ability to Track Scent

Contrary to what most scientists have thought, humans can track scents, and this ability improves with practice, finds a new behavioral study.

The study conducted at the University of California, Berkeley indicates that the human brain compares information it gets from each nostril to get clues about the location of the smell.

As people compare signals from each ear to find the source of a noise, it was initially thought that mammals can't follow smells because of their nostrils being too close together to get distinct signals.

To understand and prove the human olfactory ability, researchers made to crawl 32 blindfolded college students through grass to sniff out a chocolate-scented trail.

The trail was marked with scented twine. Blindfolded participants were equipped with thick gloves, kneepads, elbow pads and earmuffs to make sure they couldn't see, feel or hear anything.

Before the start of experiment the participants were shown a video of proper scent-tracking form, which involved putting the nose on the ground and sniffing through it.

Experts found that two-thirds of the students could follow a 30-foot trail of chocolate perfume and even changed direction precisely where the invisible path took a turn; however, nobody could do it when their noses were plugged.

Moreover, when researchers blocked their ability to smell independently with each nostril, all the 14 participants showed a dramatic drop in their scent-tracking accuracy.

Researchers found that the volunteers did better if they used two nostrils than if one nostril was taped shut.

The experimentation showed a success rate of 66 percent when both nostrils were used, as compared to 36 percent success rate with one nostril, thus supporting the idea that people benefit from having two nostrils as the brain gets stronger signals.

The researchers also found that practice made the students perfect.

Scent-tracking was aided by inter-nostril comparisons, with human nostrils sampling regions separated by about 3.5 cm.

The study will appear in the January issue of the journal Nature Neuroscience.

By revealing how noses locate smells, lead researcher Noam Sobel of the University of California, Berkeley along with graduate student Jess Porter hope to lay the groundwork for electronic noses that could detect hazards like land mines.

The study was funded in part by the U.S. Army Research Office.