It’s a movie cliche: the moment when the lost traveler intersects a set of footprints, only to realize that the prints where made by his very own boot soles. The hero then realizes, with plunging heart, that he’s been walking in circles while trying to walk a straight course through the featureless expanse. Now a small study has shown that the cliche is 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 [HealthDay News].
In the first experiment, six participants tried to follow a straight course through a forest in Germany, in an area where the land is flat and the trees quickly begin to look alike. The two subjects who walked on a sunny day stayed on a fairly straight course (as tracked by a GPS device), except for the first 15 minutes when the sun was behind the clouds. But the four who walked on an overcast day repeatedly traveled in circles, sometimes crossing their own paths after only 10 minutes. Says lead researcher Jan Souman: “They didn’t really believe when we showed them afterwards…. I think that’s certainly a point to take away, people may feel very confident about the direction where they’re going but it’s not certain” [ABC News].
In the next experiment, three volunteers strolled through the Sahara desert in southern Tunisia. The two who set out during in daylight hours did fairly well, veering from their paths but not making a looping path. The third person, who walked at night, started out on a straight path, but got derailed as soon as the moon vanished. Says Souman: “Once the moon disappeared behind the clouds, all of a sudden he turned 90 degrees, and turned 90 degrees again…. In a desert you really can walk in a straight line, if you have the sun to guide you” [ABC News].
The study, published in Current Biology, will help researchers understand how people’s senses can lead them astray when they navigate. The researchers also refuted one of the reasons that has been proposed for why people walk in circles; the theory held that most people have one leg longer or stronger than the other, which would produce a systematic bias in one direction. To test this, the researchers asked people to walk straight while blindfolded which removed the effects of vision. “Most of the participants in the study walked in circles, sometimes in extremely small ones,” Souman said [Reuters]. But the subjects didn’t consistently veer to either the left or right. Instead they drifted away from their course haphazardly in both directions, suggesting that the navigation failures had nothing to do with leg strength or length, and everything to do with general confusion.
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Image: flickr / amerune