If you're lost in the woods and you feel like you're walking in circles, you probably are.
Without landmarks to guide us, people really do go around and around, found a new study.
The finding emphasizes the importance of being prepared if you're going to set off into the wilderness or even into a maze of city streets.
"Just walking in a straight line seems like such a simple and natural thing to do, but if you think about it, it's quite complicated thing going on in the brain," said Jan Souman, a psychologist at the Max Planck Institute for Biological Cybernetics in Tubingen, Germany.
Souman's project started when a German popular-science television show approached his group with a viewer question: Why do people walk in circles when they're lost?
At first, Souman wasn't sure if that common sensation was actually true. When lost, he suspected, people might veer to the left or right. But he didn't expect them to actually walk in true circles.
To find out, he instructed nine people to walk as straight as possible in one direction for several hours.
Six walkers forged through a flat, forested region of Germany. Three trekked through the Sahara desert in southern Tunisia. (A sand storm stopped further testing in the desert). All walkers wore GPS receivers so that the researchers could analyze their routes.
The results, published today in the journal Current Biology, showed that no matter how hard people tried to walk in a straight line, they often ended up going in circles without ever realizing that they were crossing their own paths.
But there was a twist.
Circular walking befell only the four forest walkers who had to walk in overcast conditions and the one desert walker who walked at night after the moon had set. Those who could see the sun or moon managed to travel fairly straight.
Previous studies have shown that bees, pigeons and a variety of other animals move in tight circles when orienting cues like the sun are missing. The new study suggests that, whether we're conscious of what we're doing or not, people are tuned into those types of environmental signals, too.
"People find it really hard to say what they did exactly," Souman said. "It's pretty clear from our data that they do use the sun somehow."
In a follow-up experiment, the researchers challenged 15 people to walk straight while blindfolded. When they couldn't see at all, the walkers ended up going in surprisingly small circles -- with a diameter of less than 66 feet.
In repeated attempts, blindfolded walkers circled in one direction sometimes and in the opposite direction other times.
The blindfold experiment dispelled one theory -- that people might walk in circles because one leg tends to be longer or stronger than the other. Instead, Souman suspects that little mistakes in brain add up until the sense of what's straight turns into something round.
The results aren't necessarily surprising, said Randy Gallistel, a cognitive neuroscientist at Rutgers University in New Jersey. Most dead hikers, after all, are found within a mile, if not 100 meters from where they got lost.
Still, he said, if you do get lost, it's important to know that your body might end up doing the opposite of what your brain intends.
To counter the tendency to spiral, Gallistel suggested that hikers learn some simple Boy Scout tricks. Moss grows on the north side of trees. There is less vegetation on the south-facing side of a valley than on its north-facing slopes. And the sun moves from east to west throughout the day.
Better yet, bring a map and compass or GPS device.
"If you are going to move, make sure you know how to move in a straight line," Gallistel said, adding that it's hard to find a spot in the continental United States that's more than 20 miles from a road. "Straight lines are helpful. Circles don't get you anywhere."