Yes, people really do walk in circles—but only when stripped of important visual clues, such as the sun or moon, according to a paper published online today in Current Biology.

To test the common wisdom, Jan Souman, a research scientist at the Max Planck Institute for Biological Cybernetics, and his team sent test subjects out into a German forest and the Sahara Desert to see if they could follow directions to walk in a straight line—some on sunny days others on cloudy days or at night. Subjects were monitored via GPS over the course of hours (and followed by an experimenter for safety).

Those traipsing about in the sun seemed to have little trouble keeping a relatively straight course. But once the sun (or night moon) disappeared, volunteers seemed to get hopelessly lost and meandered about aimlessly—even though they believed themselves to be keeping a steady bearing. Those in the forest turned several circles, often recrossing their own path unknowingly.

"Even though walking in a straight line seems like a very simple thing to do, it's actually very complicated," Souman says. "It's not a very natural thing to do." And because researchers can't very well give verbal instructions to lab rats or birds, it's hard to know whether animals would perform any better than humans at this exercise.

The sun, it seemed was a "really important cue for direction," says Souman, who suggests people used shadows to maintain their orientation. But even that didn't present a clear-cut explanation. In the experiments, subjects were walking for a few hours at a time, during which the sun would move about 50-60 degrees, he explains. A strict adherence to the sun's location would have meant a similarly bent course, but subjects somehow did seem to correct for the movement.

To see what would happen when people were totally without visual clues, the researchers blindfolded people and turned them lose in a large field. When told to walk in a straight line, volunteers ended up heading in directions that the paper describes as "highly random" and really turning in circles—some smaller than 20 meters in diameter. The results suggest that without visual or auditory clues, people would only end up traveling a total of 100 meters from their starting point regardless of the time they are given to wander.

So why all of this walking in circles? The study was too small to make any age, gender or other demographic correlation. The randomness of the patterns—along with strength tests—ruled out the theory that people tend to favor one side or leg over the other.

Souman thinks the behavior may be a function of sensory noise—all of the information that the brain receives related to getting around, from visual, to auditory, to muscular to possibly even the feel of airflow over the skin. "There's loads of different information sources that the brain can use to determine what direction you're walking in," he explains. "They're not 100 percent accurate…and if you limit input, those small errors in signals [could] build up over time," leading people to walk in all sorts of nonsensical ways.

Souman is now trying the experiments back in the lab, where they have an omnidirectional treadmill and virtual reality goggles. His hope is so recreate some of the same navigation challenges, such as the forest, in a more controlled setting. "It's really cool to do field experiments," says Souman, whose Sahara trip was made possible by Kopfball, a television show from the West German Broadcasting Company. "But it makes it really hard to study exactly what the factors are that contribute to these behaviors."

Other researchers have demonstrated humans' impressive inability—compared with animals as humble as hamsters—to navigate without landmarks. Testing people in a virtual reality maze, for example, Brown University professor William Warren found that people wandered through "womholes" in the mazes that took them to other locations near a recognizable target, but, he told New Scientist, "people didn't even notice anything amiss."

The take-away lesson is that even those who think they have a good sense of direction shouldn't count on it—especially in the wilderness. "They shouldn't necessarily rely on their subjective senses as to whether they're walking in a straight line," says Souman. "If you're just relying on your senses, you might be fooled."

Image courtesy of Ashley Pollak via Flickr

Watch an omnidirectional treadmill experiment