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August 3, 2008

Seven Degrees Of Separation

A study conduced by researchers at Microsoft Corp. used instant messaging data to confirm the theory that it takes just under seven steps to link every one in the world. The researchers reached their conclusion based on the addresses of 30 billion instant messages sent among 180 million people worldwide during a single month in 2006. They found that, on average, any two people are linked by fewer than seven acquaintances.

The "six degrees of separation" theory has long intrigued people, even inspiring a popular 1993 movie. However, in recent years the theory had seemed to be discredited.

"To me, it was pretty shocking. What we're seeing suggests there may be a social connectivity constant for humanity," Eric Horvitz, one of the Microsoft researchers assigned to the project, said he found the results shocking, told the Washington Post.

"People have had this suspicion that we are really close. But we are showing on a very large scale that this idea goes beyond folklore."

The study, conducted by Mr. Horvitz and his colleague Jude Leskovec, used a database that covered all of the Microsoft Messenger instant-messaging network, nearly half of the world's instant-messaging traffic, in June 2006.  The study worked on the premise that two people were considered to be acquaintances if they had exchanged an instant message.

After analyzing the minimum chain lengths required to connect all the users in the database, they found the average length was 6.6, with 78% of the pairs connected in seven or fewer links.

The idea of six degrees of separation originated with Stanley Mailgram, an academic social psychologist in the U.S., after his research asking people to pass a letter only to others they knew by name.  The goal was to have the letter reach a named person they did not know living in another city.   Mailgram found that the average number of times the letter was passed on was six, and thus coined his  "six degrees of separation" theory.

However, in July 2006, Judith Kleinfeld, a psychology professor at Alaska Fairbanks University, reviewed Milgram's original research notes and found that 95% of the letters that were sent out had failed to reach their intended target.  At that time, Kleinfeld suggested the theory might be the academic equivalent of an urban legend.

Horvitz and Leskovec reported that, to their knowledge, their study was the first to confirm Milgram's theory on a global scale.

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