London, June 5 : A team of researchers from Northeastern University in Boston, Massachusetts, has worked out some apparently universal laws of human motion by tracking the signals from 100,000 mobile-phone users, who sent and received calls and text messages during the study.
The researchers say that their findings may have implications for predicting how viruses could spread through populations, and thus may be helpful for urban planners and traffic forecasters in allocating resources.
During the study, Albert-Laszlo Barabasi and his colleagues observed that most people are habitual of making regular trips to the same few destinations like work and home, and pepper them with occasional longer forays like vacations.
The researchers found that the distance covered by people differed widely between individuals.
However, people still followed a similar pattern, they added.
While most people moved on average a short distance on a daily basis, some moved long distances in short time.
Barabasi said that though the patterns sounded obvious, scientists had been unable to study them precisely to date because of the difficulties involved in obtaining data on individual human movements.
"We don't really know how humans move around. When you look at the population as a whole, there is no way of describing the patterns. The problem with answering this question is that people normally are not tracked - but today we are tracked thanks to the phones we carry with us," Nature magazine quoted him as saying.
He revealed that he and his colleagues collaborated with a mobile company for their study, and obtained from the service provider anonymized data on which transmitter towers had handled the calls and texts for 100,000 individuals over the course of six months.
Barabasi said that the findings of their analysis were consistent with a 2006 study wherein human movements were attempted to be tracked using banknotes as a proxy measure.
He revealed that the researchers involved in that study analysed the movements of over half a million US one-dollar bills as they were passed around over five years, and found similar patterns of lots of short movements and occasional longer ones.
The researcher, however, pointed out that banknotes would usually pass from person to person rarely staying in the same pocket for long, and thus the previous study could only derive an average picture of movement.
Dirk Brockmann of Northwestern University in Illinois, who carried out the banknotes study, said that Barabasi's study "answers questions about individual variability that we were unable to address with the dollar bills."
He revealed that it was due to strict data-protection laws that he could not conduct his own version of the mobile-phone study in Germany.
He further said that mobile-phone data could help obtain information regarding where individuals live and work.
"I've been trying to get my hands on mobile-phone data but it isn't possible," he said.
Barabasi dealt with privacy considerations by not revealing where in the world the data were from.
Brockmann says that the challenge now is to find out why something as complex as human movement follows such consistent patterns.
"Neither study can answer that question," he said.