Mobile phones expose human habits

The whereabouts of more than 100,000 mobile phone users have been tracked in an attempt to build a comprehensive picture of human movements.
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.
"This is just the tip of the iceberg," he told BBC News.
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Researchers have previously attempted to map human activity using GPS or surveys, but it is expensive.
One innovative approach tracked the movement of dollar bills in an attempt to reconstruct human movements.
The study used data from the website wheresgeorge.com, which allows anyone to track a dollar bill as it circulates through the economy. The site has so far tracked nearly 130 million notes.

All of the mobile phone data was collected anonymously
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.
The researchers said they were "not at liberty" to disclose where the information had been collected and said steps had been taken to guarantee the participants anonymity.
For example, individual phone numbers were disguised as 26 digit security codes.
"Furthermore, we only know the coordinates of the tower routing the communication, hence a user's location is not known within a tower's service area," they wrote.
Each tower serves an area of approximately 3 sq km.
Information was collected for six months. But, according to the researchers, a person's pattern of movement could be seen in just three.