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August 03, 2010

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Unguided, we really do go in circles, study finds

Aug. 20, 2009
Courtesy Cell Press
and World Science staff

Just as pop­u­lar wis­dom holds, peo­ple try­ing to walk a straight course through un­fa­mil­iar ter­ri­to­ry end up walk­ing in cir­cles, ac­cord­ing to a new stu­dy.

Al­though that be­lief has per­vad­ed pop­u­lar cul­ture, there has been no sci­en­tif­ic ev­i­dence to back it up un­til now, ac­cord­ing to the re­search­ers, whose re­port ap­pears on­line Aug. 20 in the jour­nal Cur­rent Bi­ol­o­gy.

Peo­ple try­ing to walk a straight course through un­fa­mil­iar ter­ri­to­ry really do end up walk­ing in cir­cles, ac­cord­ing to a new stu­dy. (Im­age cour­tesy W. W. Skies)
“The sto­ries about peo­ple who end up walk­ing in cir­cles when lost are ac­tu­ally true,” said Jan Sou­man of the Max Planck In­sti­tute for Bi­o­log­i­cal Cy­ber­net­ics in Ger­ma­ny, an author. 

“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.” 

Those cir­cu­lar paths are rarely sys­tem­at­ic, the in­ves­ti­ga­tors found. A per­son may veer to the left, then again to the right, be­fore end­ing up back where they started, Sou­man said. That rules out one ex­plana­t­ion for the phe­nom­e­non: that circle-walk­ing stems from some sys­tem­at­ic bi­as to turn in one di­rec­tion, such as dif­fer­ences in leg length or strength.

It seems that the cir­cles rath­er emerge nat­u­rally through “ran­dom drift” in where an in­di­vid­ual thinks straight ahead to be, Sou­man said.

The re­search­ers tested the idea in both for­est and des­ert en­vi­ron­ments. Par­ti­ci­pants were in­structed to walk as straight as they could in one di­rec­tion, and their tra­jec­to­ry was recorded via GPS. Six peo­ple walked for sev­er­al hours in a large, flat for­est—four on a cloudy day with the sun hid­den. 

Those four all walked in cir­cles, with three of them re­peat­edly cross­ing their own paths with­out no­tic­ing it. 

When the sun was out, two oth­er par­ti­ci­pants fol­lowed an al­most per­fectly straight course, ex­cept dur­ing the first 15 min­utes, when the sun was still hid­den be­hind some clouds. 

Three oth­er par­ti­ci­pants walked for sev­er­al hours in the Sa­hara des­ert, in south­ern Tu­ni­sia. Two of them, who walked dur­ing the heat of the day, veered from the course they were in­structed to fol­low but did not walk in cir­cles. The third walked at night, at first by the light of a full moon. Only af­ter the moon dis­ap­peared be­hind the clouds did he make sev­er­al sharp turns, bring­ing him back in the di­rec­tion he started from.

In oth­er tests, blind­folded peo­ple walked in sur­pris­ingly small cir­cles, though rarely show­ing a ten­den­cy to trav­el in any par­tic­u­lar di­rec­tion.

Souman’s group plans to study the ten­den­cy un­der more con­trolled con­di­tions by ask­ing peo­ple to walk through a virtual-real­ity for­est on a spe­cially built tread­mill, which al­lows a per­son to go in any di­rec­tion. These tests would let re­search­ers iso­late the var­i­ous fac­tors that might play a role, such as the avail­abil­ity of the sun or oth­er land­marks, and to study their con­tri­bu­tions to walk­ing straight—or in cir­cles.

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Just as popular wisdom holds, people trying to walk a straight course through unfamiliar territory really do end up walking in circles, according to a new study. Although that belief has pervaded popular culture, there has been no scientific evidence to back it up until now, according to the researchers, whose report appears online Aug. 20 in the journal Current Biology. “The stories about people who end up walking in circles when lost are actually true,” said Jan Souman of the Max Planck Institute for Biological Cybernetics in Germany. “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.” Those circular paths are rarely systematic, the investigators found. A person may sometimes veer to the left, then again to the right, before ending up back where they started from, Souman said. That rules out one explanation for the phenomenon: that circle-walking stems from some systematic bias to turn in one direction, such as differences in leg length or strength. It seems that the circles rather emerge naturally through “random drift” in where an individual thinks straight ahead to be, Souman said. The researchers tested the idea in both forest and desert environments. Participants were instructed to walk as straight as they could in one direction, and their trajectory was recorded via GPS. Six people walked for several hours in a large, flat forest—four on a cloudy day with the sun hidden. Those four all walked in circles, with three of them repeatedly crossing their own paths without noticing it. When the sun was out, two other participants followed an almost perfectly straight course, except during the first 15 minutes, when the sun was still hidden behind some clouds. Three other participants walked for several hours in the Sahara desert, in southern Tunisia. Two of them, who walked during the heat of the day, veered from the course they were instructed to follow but did not walk in circles. The third walked at night, at first by the light of a full moon. Only after the moon disappeared behind the clouds did he make several sharp turns, bringing him back in the direction he started from. In other tests, blindfolded people walked in surprisingly small circles, though rarely showing a tendency to travel in any particular direction. Souman’s group plans to study the tendency under more controlled conditions by asking people to walk through a virtual-reality forest on a specially built treadmill, which allows a person to go in any direction. These tests would let researchers isolate the various factors that might play a role, such as the availability of the sun or other landmarks, and to study their contributions to walking straight—or in circles.