Six Degrees of Separation: Do We Really Live in a ‘Small World’?
Arguments about the interconnectedness of human society have received a shot in the arm with the publication of a new study of 30 billion instant messaging conversations between 240 million people around the world.
Microsoft researchers claim their results support Milgram's idea that each of us is only 'six degrees of separation' away from anyone else on the planet.1
It was back in the 1960s that social psychologist Stanley Milgram found that he could send a letter to a random person in Nebraska or Boston and have it reach a random target person in Massachusetts.
The letter asked the first random receiver to forward it to someone who might be more likely to know the target person, but it had to be someone they were on first-name terms with. So, for example, if the first recipient, who lived in Nebraska, knew anyone at all in Massachusetts, they would send it to them. Then on and on it would go until it reached the target.
Milgram found that on average it would take 5.2 intermediaries for his letter to go from the first person to its destination, via each person's social network.
Six degrees of Kevin Bacon and Paul Erdos
Milgram took this study, along with other research, to demonstrate that we really do live in a small world. Milgram's work eased itself into the popular imagination with it's optimistic message that each of us is only a few social steps away from everyone else in the world.
The theory inspired the trivia game 'Six Degrees of Kevin Bacon' in which participants try to link any given actor back to an appearance with Kevin Bacon in as few moves as possible. Mathematicians also have a version in which they trace each other back to the eccentric Hungarian mathematician Paul Erdos through shared publications.
Milgram's work has been challenged, though, by Professor Judith Kleinfeld who found, when re-examining Milgram's work, that there were problems with his method. For example he used relatively prominent people in society as the start and end points for his chain letter, plus a very high percentage of letters never arrived at their destination at all. Subsequent replications of Milgram's work are also few and far between and don't test links across class or geographical boundaries.
Kleinfeld points out that Milgram's claim for the six-degrees of separation could be an academic myth. Real life is probably not as incestuous as the worlds of actors or mathematicians.
Small world of email
In 2003, though, some support for Milgram's idea was found by Duncan Watts and colleagues at Columbia University, in a paper published in Science. Emailers were asked to try and forward a message to one of 18 target people in 13 different countries, going via their friends and acquaintances. All together more than 60,000 people took part. They found that successful chains were completed in between 5 and 7 steps, similar to Milgram's results.
Unfortunately this email replication had the same problem as Milgram's original study - many chains simply broke down. Also, like Milgram's study, the targets were relatively visible in society, one was a vet, another a policeman, another a technology consultant. Where are the factory operatives or convenience store workers in this sample?
New study: 6.6 degrees of separation
But a new study carried out by Leskovec and Horvitz for Microsoft Research addresses some of these points since they used data that cuts across geographical and class boundaries. They analysed data collected by Microsoft from 30 billion instant messages sent around the world in one month in 2006.
Examining this data - the largest social network ever analysed - they found that the average number of hops between any two instant messenger users was 6.6 - slightly higher than Milgram's finding.
Leskovec and Horvitz claim their work supports Milgram's theory that each of us is only separated from anyone else by six jumps. The problem, though, is that it is hard to generalise from an online to an offline environment. People behave differently online than they do offline:
- The biggest problem is Leskovec and Horvitz's assumption that instant messaging between two people can be considered a marker of a relationship. For example, I speak to the postman but he's not really part of my social network - certainly not in the sense Milgram meant. The data is likely to over-estimate how much instant messaging between two people can be considered a marker of a 'relationship'.
- A related problem is that people are more disinhibited online. They are more likely to say or do what they want rather than feel social pressure to keep quiet or conform. Consequently people may be more likely to talk online to people through instant messenger that in the real world they wouldn't. This could easily inflate online social networks.
These are just a couple of the main problems - others include a skew towards younger people and the data, by its very nature, only taking into account more highly developed, computer-literate groups in society.
Small world?
There are all sorts of reasons that we may want to believe Milgram's small world conclusions, as Kleinfeld herself points out. If we really are so easily connected to others our lives seem less isolated, cold and forbidding.
Both Milgram's and Watts and colleagues' studies seem to support the small world theory but it is hard to draw solid conclusions when so many chains of communication broke down in both studies. It's difficult to know whether these chains were broken because of apathy or because the messages reached a cul-de-sac in a social network.
It's probably over-stretching the new research by Leskovec and Horvitz to claim it supports Milgram's idea of six (or seven) degrees of separation in the offline world. We'll have to wait for an equivalent offline study before we can truly say it is a small world. Until then we'll have to be content with playing Six Degrees of Kevin Bacon (and Paul Erdos for mathematicians) which rely on much more intimate social networks.
Notes
1Milgram himself never used the phrase 'six degrees of separation'.
[Image credit: social d]
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So you're telling me all those chain letter emails that said Microsoft was paying people to forward and track the message were real? I could have been rich.
So I wonder how close everyone is to say a tribal member of an aborigine group or a amazon peoples leader??? So Ill try to find a name and we can all see.
So when it says that Microsoft analyzed over 30 billion instant messages, does that mean that they were reading other peoples instant messages?
I was introduced to the trivia game "Six Degrees of Kevin Bacon", a while back and i didn't think much of it. I just thought it was some game that didn't really go into much depth and was good to kill time. It is kind of surprising that a game like that inspired a theory that everyone is connected somehow. Although Milgrams, Leskovich and Horvitz experimental findings are not certain enough. I still like to believe that everyone is connected by at least 6 people worldwide. Who knows i could be linked to Scarlette Johanson.
Ray L.
What an amazing blog!
My husband was a law enforcement officer in another town in a very distant part of our state. Since then, he has moved, married, worked several other jobs, then was overtaken by a mental illness.
It was pretty funny, though, we now live 300 miles away from where he began his law enforcement career. I work with severely mentally ill people in our town. DH, in attempting to recover from his mental illness, joined a support group. In that support group was a man that I worked with on a regular basis (he was a client of mine). Since they were the only two men in the group, they were "partners" for a few exercises. They started talking, and it turns out that DH had arrested the other man 18 years ago, in the town that was 300 miles away. They both remembered it, because the man who got arrested was very violent and out of control. He remembered my husband, and my husband remembered him. Small world, for sure!
Gute Arbeit hier! Gute Inhalte.
I just watched this program on the science channel and was more interested in the hub and DNA-protien and the potential good this may do for our small planet. I think we are all connected in ways with all things on this earth and are just beginning to get a clue.