Movement and call data showed a different picture of connectivity than surveys

Friendships can be inferred with 95% accuracy from call records and the proximity of users, says a new report.

Researchers fitted 94 mobiles in the US with logging software to gather data.

The results also showed that those with friends near work were happier, while those who called friends while at work were less satisfied.

The data, published in Proceedings of the National Academy of Sciences, showed a marked contrast with answers reported by the users themselves.

"We gave out a set of phones that were installed with a piece of 'uber-spyware'," said the study's lead author Nathan Eagle, now at the Santa Fe Institute.

"It's invisible to the user but logs everything: communication, users' locations, people's proximity by doing continuous Bluetooth scans."

The researchers then compared the data with results from standard surveys given to the mobile users - and found, as the social sciences have found time and again, that people reported different behaviour than the mobile data revealed.

Wide application

One principal question of such a small sample size, made up exclusively of students from the Massachusetts Institute of Technology, is how much the results really mean in a sociology context.

However, the group has gone on to carry out a larger study that just finished, comprising 1,000 people in Helsinki, Finland.

"Suddenly all our subjects became unpredictable; they all flooded into downtown Boston to a rally in the centre of the city.

"City planners approached us because they wanted to know how people were using urban infrastructure, to know when the people left the rally, how many walked across the bridge and how many took the subway, how many biked or took the bus.