Human habits tracked by mobile phones

The study concludes that humans are creatures of habit, mostly visiting the same few spots time and time again.

Most people also move less than 10km on a regular basis, according to the study published in the journal Nature.

The results could be used to help prevent outbreaks of disease or forecast traffic, the scientists said.

"It would be wonderful if every [mobile] carrier could give universities access to their data because it's so rich," said Dr Marta Gonzalez of Northeastern University, Boston, US, and one of the authors of the paper.

Dr William Webb, head of research and development at the UK telecoms regulator, Ofcom, agreed that mobile phone data was still underexploited.

Studies such as this suggested that humans wander in an apparently random fashion, similar to a so-called "Levy flight" pattern displayed by many foraging animals.

However, Dr Gonzalez and her team do not believe this approach gives a complete picture of people's movements.

"The bills pass from one person to another so they can't measure individual behaviour," she explained.

The new work tracked 100,000 individuals selected randomly from a sample of more than six million phone users in a European country.

Each time a participant made or received a call or text message, the location of the mobile base station relaying the data was recorded.

Model behaviour

"The vast majority of people move around over a very short distance -
around five to 10km," explained Professor Albert-Laszlo Barabasi,
another member of the team.

"Then there were a few that moved a couple of hundred kilometres on a regular basis."

The results showed that most people's movements follow a precise mathematical relationship - known as a power law.

Nokia believes phones could be fitted with sensors to collect data

"That was the first surprise," he told BBC News.

The second surprise, he said, was that the patterns of people's
movements, over short and long distances, were very similar: people
tend to return to the same few places over and over again.

"Why is this good news?" he asked. "If I were to build a model of how
everyone moves in society and they were not similar then it would
require six billion different models - each person would require a
different description."

Now, modellers had a basic rule book to follow, he said.

"This intrinsic similarity between individuals is very exciting and it has practical applications," said Professor Barabasi.

For example, Professor John Cleland of the London School of Hygiene and
Tropical Disease (LSHTM) said the study could be of use to people
monitoring the spread of contagious diseases.

"Avian flu is the obvious one," he told BBC News. "When an outbreak of
mammalian infectious airborne disease hits us, the movement of people
is of critical concern."

Dr Gonzalez said that traffic planners had also expressed an interest in the study.

Sensor overload

Although the scale of the latest study is unprecedented, it is not the
first time that mobile phone technology has been used to track people's
movements.

Scientists at MIT have used mobile phones to help construct a real-time
model of traffic in Rome, whilst Microsoft researchers working on
Project Lachesis are examining the possibility of mining mobile data to
help commuters pick the optimum route to work, for example.

Location data is increasingly used by forensic scientists to identify the movements of criminal suspects.

For example, the technique was used by Italian police to capture
Hussain Osman, one of four men jailed for the failed suicide bombings
in London on 21 July.

Commercial products also exist, allowing parents to track children or
for friends to receive alerts when they are in a similar location.

These types of services and projects will continue to grow, Dr Webb
believes, as researchers and businesses find new ways to use the mobile
phone networks.

"There are so many sensors that you could conceivably attach to a phone
that you could do all kinds of monitoring activities with," he said.

For example, Nokia have put forward an idea to attach sensors to phones
that could report back on air quality. The project would allow a large
location-specific database to be built very quickly.

Ofcom is also planning to use mobiles to collect data about the quality of wi-fi connections around the UK.

"I am sure there will be tens if not hundreds of these ideas emerging over the next few years," said Dr Webb.