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.
"The significance of the experiment is that it shows how important senses are for navigating," Sanberg said. "It's showing scientifically what we had known anecdotally."
When flying into clouds, pilots who think they're flying straight can
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