Facebook cuts six degrees of separation to four

Since the American social psychologist, Stanley Milgram, conducted his famous ‘small world experiment’ in the 1960s, it has been commonly accepted that most people have six degrees of separation between them.

However, a vast new study by Facebook’s data team and the University of Milan, which assessed the relationships between 721 million active users (more than 10 per cent of the global population) of the social network, has found that the average number of connections between people has dropped to four.

The huge piece of research, which took a month to conduct and analysed 69 billion connections across the site, found that 92 per cent of facebook users are connected by only 5 hops, or four degrees of separation.

“Using state-of-the-art algorithms…we were able to approximate the number of ‘hops’ [degrees of separation] between all pairs of individuals on Facebook.

“We found that six degrees actually overstates the number of links between typical pairs of users: While 99.6% of all pairs of users are connected by paths with 5 degrees (6 hops), 92% are connected by only four degrees (5 hops),” the Facebook Data team said.

Facebook has become the world’s largest social network, with more than 800 million members. The team found that as the site has grown; representing an ever larger fraction of the global population, the degrees of separation between people has been falling.

The average distance between all people on the site in 2008 was 5.28 degrees, while now it is 4.74.

The connectivity that social networks have brought means that someone on Facebook in Siberia or the Peruvian rainforest is probably no more than a friend of a friend of a friend of a friend of a friend.

Professor Richard Wiseman, a psychologist at the University of Hertfordshire, said sites such as Facebook and Twitter had provided a mechanism which allowed more people to be in touch at the same time around the world.

“I think Facebook and Twitter have allowed people a tool by which they can be in touch with far more people than ever before. These sites have also brought groups of people together with the same interests, who don’t always know each other. It’s like the difference between living in a city versus a rural community. People can now find each other with greater ease than ever before.

“However, people may now have more contacts, but that should not be confused with the number of actual ‘friends’ they have,” he cautioned.

Wiseman said that it would be dangerous to conclude from the study that people had more real friends because of social networks, and therefore were actually closer to a greater number of people.

“I doubt the algorithms, which were used to create this research, took into account how many people out of user’s list of ‘friends’ were actually people they knew personally. The six degrees of separation research was all about people who knew each other forming a chain. This is loosening that term.”

The Facebook analysts also found that when they just looked at people’s connections in a single country, most pairs of people are only separated by three degrees.

In Milgram’s original experiment, he famously tested the idea that any two people in the world are separated by only a small number of intermediate connections. By sending packages to 160 random people, asking them to forward the parcel to the friend or acquaintance that had the best chance of getting it to a set final person, he found that people in the United States were connected via an average of 5.5 others.

This gave rise to the “six degrees of separation” theory in popular culture.

A game loosely based on the “six degrees of separation” theory and the small world experiment has also thrived online. In “six degrees of Kevin Bacon”, players have to link any actor to Kevin Bacon in as few steps as possible.