THURSDAY, Aug. 20 (HealthDay News) -- Stories abound of adventurers losing their way in the wilderness, unwittingly walking in circles for days.
Now, new research confirms that the anecdotes are true. Without the sun, a compass or a landmark, people trying to follow a straight course through a forest or a desert ended up back where they started, according to a study published online Aug. 20 in Current Biology.
"Our results confirm the stories that are often described in films and books: people often walk in circles when they are lost," said study author Jan Souman, of the Max Planck Institute for Biological Cybernetics in Germany. "Second, our results show that even something seemingly very simple as walking in a straight line actually involves a complicated interplay between several senses, our motor actions and cognition."
In the first experiment, researchers instructed six participants to walk as straight as they could through a large, flat forest, a place in which one tree could quickly look very much like another.
Four participants, walking on a day in which the sun was hidden behind a thick cloud cover, all went in circles, with three participants unintentionally crossing their own path several times.
Two participants walked through the forest on a sunny day. With the sun to guide them, they followed an almost perfectly straight course, as measured by a global positioning system (GPS), except during the first 15 minutes, when the sun was still hidden behind the clouds.
Next, researchers had three people walk in the Sahara desert. Two participants who walked when the sun was out veered from a straight line, but did not walk in a circle.
A third participant walked at night. As soon as the moon disappeared behind clouds, the walker made several sharp turns and started heading back in the direction from which he came.
In a third experiment, researchers had participants attempt to walk a straight line through a grassy field while blindfolded for 50 minutes. Not only did they walk in circles, some of the circles were as small as about 66 feet, similar in size to a basketball court.
"People cannot walk in a straight line if they do not have absolute references, such as a tower or a mountain in the distance or the sun or moon, and often end up walking in circles," Souman said.
Theories about circle-walking include the concept that each person has a bias to turn in one direction because of subtle differences in the strength or length of one leg over the other.
But in the study, participants drifted left or right, and often reversed course, without seeming to favor either direction.
So why do people travel in circles without visual guideposts?
Walking in a straight line is actually a complex task involving the brain, sense of sight, proprioception (the sense of where parts of the body are located relative to each other in space), and the vestibular system, which is involved with spatial awareness and sense of balance, Souman said.
When those are disrupted, people tend to drift randomly, often passing through the place where they started, the study authors noted.
"Our results show that even when people feel they are very certain that they are walking in the correct direction, they still can be very wrong," Souman said. "We cannot always trust our senses."
Paul Sanberg, director of the University of South Florida Center for Aging and Brain Repair, said the study has important implications for pilots and sailors.