Berkeley, Calif. – Since the most ancient humans lifted their noses from the ground and stood upright, humanity’s sense of smell has dwindled to second- class status, a talent we gladly leave to drug-sniffing dogs.
But a new study suggests that buried in each person’s olfactory lobe lurks enough tracking skill to make a bloodhound bay with resentment.
If the results are surprising, that may be because no one ever tried putting a bunch of college undergraduates in a field wearing blindfolds and sound-muffling headphones, then had them crawl in the grass after a scent like pigs hunting for truffles.
When researchers at the University of California at Berkeley did try that, they found that most of the students could follow a 30-foot trail of chocolate perfume and even changed direction precisely where the invisible path took a turn.
What’s more, the subjects were able to smell in stereo; when researchers blocked their ability to smell independently with each nostril, the students’ scent-tracking accuracy dropped off drastically.
By revealing how noses locate smells, the scientists hope to lay the groundwork for electronic noses that could detect hazards such as land mines. Their work, published online Sunday in the journal Nature Neuroscience, was funded in part by the U.S. Army Research Office.
Other experts say the findings will help rebut the misconception that people stink at following scents.
“What this study highlights most for me is that the human sense of smell is a lot better than many people think it is,” said Jay Gottfried, a professor of neurology at Northwestern University.
Smell is critical to taste
Our dormant flair for smell comes as no surprise to many researchers who study perception. Humans need a good sense of smell to distinguish flavors, which arise only partly from the taste buds on the tongue. Without smell, people would have little ability to tell apart the flavors of fruits or types of meat.
Granted, we’ll never match the prowess of nature’s specialty smellers, such as rats or German shepherds. Other animals have bigger snouts to gather scents and more brain area devoted to processing smells, not to mention the built-in advantage of four-legged creatures that constantly put their noses to the ground. While it took the Berkeley students up to 10 minutes to navigate the scent path, a dog could do the same in seconds.
In order to focus on the students’ olfactory ability, the researchers put together an outfit that one likened to a mobile sensory-deprivation chamber, with taped-over goggles, earmuffs and thick work gloves to block anything but smell from guiding their way. They also wore devices over their noses to control how much scent each nostril could take in and to measure how fast they were sniffing.
Decked out in full regalia, the students resembled members of an exotic humanoid species.
“We drew lots of crowds,” said study lead author Jess Porter, a graduate student at Berkeley’s neuroscience institute.
A major reason the scientists studied human subjects is that people are more willing than animals such as dogs to put up with all the extra equipment the study required.
“Dogs really don’t like having things in their nostrils,” said co-author Noam Sobel, an associate professor at Berkeley.
Humans zigzag like dogs
To create a scent trail, the scientists soaked a line of string in the chocolate scent and embedded it in the grass. The people were set loose on the ground about 9 feet from the trail, then had to find the scent and follow it.
Faced with a tracking task that virtually no person ever has to do, the humans quickly adopted some of the same habits that dogs use. They zigzagged as they tracked the smell, much like hunting dogs following a pheasant – in fact, dogs typically veer off a trail more than the human subjects did. Scientists have seen similar behavior among crabs following scent plumes underwater.
Although no one knows for sure why zigzagging is important, one theory is that tracking animals, including people, try to keep a sense of where the boundary of the smell is so they don’t lose the trail.
“You want to maximize your chances of noticing when the track is going to turn,” Porter said.
A key observation was that the people did better at tracking when they could sense distinct smells in each nostril. When the subjects wore a device that channeled the same air into both nostrils, their performance lagged.
The researchers said the contribution of the two nostrils is similar to the way having two ears lets us find a sound’s origin.
“When someone drops a coin on the ground, you immediately know where to turn,” Gottfried said. “That’s because your brain computes the difference in when the sound arrives at each ear and extracts information about where the coin fell.”
The same holds true for scents, he said.
