WASHINGTON — Researchers secretly tracked the locations of 100,000 people outside the U.S. through their cellphone use and concluded that most people rarely stray more than a few miles from home.
The first-of-its-kind study by Northeastern University raises privacy and ethical questions for its monitoring methods, which would be illegal in the United States.
It also yielded somewhat surprising results that reveal how little people move around in their daily lives. Nearly three- quarters of those studied mainly stayed within a 20-mile-diameter circle for half a year.
The scientists would not say where the study was done, describing the location only as an industrialized nation.
Researchers used cellphone towers to track individuals’ locations whenever they made or received phone calls and text messages over six months. In a second set of records, researchers took 206 cellphones that had tracking devices and got their locations every two hours for a week.
The study was based on cellphone records from a private company, whose name also was not disclosed. Study co-author Cesar Hidalgo, a physics researcher at Northeastern, said he and his colleagues didn’t know the individual phone numbers.
That type of nonconsensual tracking would be illegal in the United States, according to Rob Kenny, a spokesman for the Federal Communications Commission. Consensual tracking, however, is legal and even marketed as a special feature by some U.S. cellphone providers.
The study, published today in Nature, opens up the field of human-tracking for science and calls attention to what experts said is an emerging issue of locational privacy.
“This is a new step for science,” said study co-author Albert-Lazlo Barabasi, director of Northeastern’s Center for Complex Network Research. “For the first time, we have a chance to really objectively follow certain aspects of human behavior.”
Hidalgo said researchers were not required to check with an ethics panel because the experiment involved physics, not biology. However, had they done so, they might have gotten an earful, suggested bioethicist Arthur Caplan at the University of Pennsylvania.
“There is plenty going on here that sets off ethical alarm bells about privacy and trustworthiness,” he said.
Studies done on normal behavior at public places is “fair game for researchers” as long as no one can figure out identities, Cap lan said in an e-mail.
“But my cellphone is not public. My cellphone is personal,” Caplan wrote. “Tracking it and thus its owner is an active intrusion into personal privacy.”
Hidalgo said the people tracked in the study are more statistics than examples.
“In the wrong hands, the data could be misused,” Hidalgo said. “But in scientists’ hands, you’re trying to look at broad patterns. . . . We’re not trying to do evil things. We’re trying to make the world a little better.”
