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Dec. 18, 2006 -- Humans can track a scent trail across a field, with all their other senses blocked, a new study shows.
The findings, published in Nature Neuroscience, suggest the human sense of smell doesn't get enough credit, write the researchers.
They include Jess Porter and Noam Sobel, PhD, of the University of California, Berkeley. Porter is a biophysics graduate student, Sobel an associate professor in the university's Helen Wills Neuroscience Institute and psychology department.
Studying the Human Sense of Smell
The study looked at 46 healthy young adults aged 18 to 26.
The participants wore masks that blocked their vision; earmuffs that screened out sounds; and gloves, knee pads, and elbow pads to mute their sense of touch.
Wearing all that gear, they crawled on their hands and knees in an open field to try to find and follow a scent trail.
The trail had been made from twine dipped in chocolate essential oil and was 32 feet long. It consisted of two straight segments with a 45-degree turn.
Participants began the test nearly 10 feet from the start of the trail.
They had 10 minutes to find and sniff their way to the end of it, with no feedback to tell them how they were doing.
Better by a Nose
Thirty-two people took the test with both nostrils open. Two-thirds were able to follow the trail.
Another 14 people took the test again -- after the course had been changed -- with one nostril taped shut. Only 36% completed that test.
Then, four participants trained on the scent trail.
They crawled along the chocolate scent trail three times a day over three days during a two-week period. The researchers kept changing the course to make sure participants didn't memorize it.
The training paid off. The practiced participants wandered off course less often and more than doubled their speed at completing the course.
In general, these humans whiffed and sniffed for the scent trail much like dogs do, the study shows.
However, bloodhounds are in no danger of losing their job. Dogs still sniff faster -- which may help explain why dogs are more often used for scent tracking than people.
SOURCES: Porter, J. Nature Neuroscience, Dec. 17, 2006; advance online edition. News release, Nature and the Nature Research Journals.