By Alan Mozes
Wednesday, June 4, 2008 12:00 AM
WEDNESDAY, June 4 (HealthDay News) -- Using cell phone records to track movement, a new study suggests that people are creatures of habit, spending most of their time going to -- and remaining at -- a few key locations, such as work and home.
The researchers said their novel approach to analyzing human mobility appears to be more accurate, easier, and cheaper than prior efforts based on tracking, for example, the movement of money. And, they added, the cell phone model could prove helpful to epidemiologists seeking to improve planning for emergency responses to natural disasters and disease outbreaks.
"Mobility patterns are very important to quantify, because they affect everything from epidemic forecasting to urban road planning," said study lead author Marta C. Gonzalez, a professor at Northeastern University's Center for Complex Network Research. "But despite a big interest, there's been a lack of data, because it's very hard to track movement."
Gonzalez and her colleagues published their findings in the June 5 issue of the journalNature.
They said their observation of repetitive and controlled mobility departs somewhat from a traditional paradigm regarding more random animal movement, known as the "Levy flight" pattern. This model was based on typical food searching behavior, which mostly consisted of non-repetitive, short-distance foraging, interspersed with the occasional longer trip.
For the study, the researchers analyzed cell phone transmitter tower logs, which track mobility within a defined tower zone. The average tower zone was about two square miles, although more than 30 percent of the zones covered an area of less than one square mile.
Information was collected on the movements of approximately 100,000 randomly selected people over a six-month period.
Gonzalez and her team found that most mobile phone users traveled only short distances, although a few consistently moved across distances of hundreds of miles. Also, regardless of whether a person routinely traveled to just five locations or 50, most devoted about 70 percent of their time to just two repeatedly visited destinations.
"Because we only have information as to tower zones, we can't say for certain exactly which location people are going to," Gonzalez said. "But we assume, of course, that the two preferred locations are a person's place of work and their home."
Karen L. Kramer, an associate professor at Harvard University's department of biological anthropology, said that, despite the study's findings that people today are creatures of habit, flexibility in movement has always been central to human mobility and, in turn, human survival.
"As humans, we have always monitored our changing resources and moved about accordingly," she said. "Humans are really good at this, and the ability to do this well -- to adapt our movements to a changing environment -- is really critical to the human success story, because mobility serves as a means to gather vital information about the world. It's our security net."
She acknowledged, however, that as modern "hunter-gatherers" have abandoned the daily tracking of watering holes and food sources, gathering points may have become more localized and reliable.
"If we're living in a city, we go to a job so we can get money to buy food, and then, we go to the store to buy the food, and then, we bring the food home to eat," she said. "So, we're still, essentially, hunters and gatherers. But, of course, if the resources are concentrated, then mobility will be as well."
To learn more about human mobility, visit The John D. and Catherine T. MacArthur Foundation.
SOURCES: Marta C. Gonzalez, Ph.D., department of physics and Center for Complex Network Research, Northeastern University, Boston; Karen L. Kramer, Ph.D., associate professor, department biological anthropology, Harvard University, Cambridge, Mass.; June 5, 2008,Nature