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Six Degrees of Separation? Facebook Finds a Smaller Number


Pedestrians pass by One World Trade Center in 2015. Facebook users are more closely connected than people are commonly thought to be, according to a new blog post. Credit Michael Nagle for The New York Times

Facebook ran the numbers and concluded that we are all much closer than the traditional “six degrees of separation.”

The social media giant released a report on its blog Thursday announcing each person in the world is separated from every other by “an average of three and a half other people.”

The number six in “six degrees” generally refers to the number of links in the chain of acquaintances, seven people in all. The phrase proposes that between any two strangers there are at most five intermediaries that link them together. So according to Facebook, depending on how you want to do the counting, the true number, referring to intermediaries or to links, is either 3.57 or 4.57 degrees of separation.

The new statistic is as much a testament to the growing popularity of Facebook as it is to a steadily shrinking human social world. The calculation includes only connections between the network’s 1.59 billion users, ignoring the approximately 5.7 billion other humans who have yet to set up accounts. (In July, the United Nations estimated that the current world population to be 7.3 billion.)

If you are logged into Facebook, the blog post will tell you your average degree of separation “from everyone.” The number is an estimate derived from statistical algorithms and not, as it seems, an intrusive estimate of the reach of your friends and family. According to the post, Facebook users in the United States are connected by an average of 3.46 people.

It placed my personal degree of connections at 3.2, below average but nowhere close to the reach of Sheryl Sandberg, who, the post says, is separated from “everyone” by only 2.92 degrees.

The six degrees of separation theory has always been more thought experiment than scientific fact. Its invention is most often credited to the Hungarian writer Frigyes Karinthy, who, in 1929, used a short story to consider the fact that “Planet Earth has never been as tiny as it is now.”

In the philosophical piece, similar in its approach to the work of Jorge Luis Borges and César Aira, Mr. Karinthy had his characters propose a game of connection, choosing strangers such as a Nobel Prize-winning writer and a worker for the Ford Motor Company and forging lines of acquaintance between themselves and those subjects.

“Nobody from the group needed more than five links in the chain to reach, just by using the method of acquaintance, any inhabitant of our planet,” he wrote.

The playwright John Guare took up the idea in 1990, writing a play titled “Six Degrees of Separation,” which was adapted three years later into a movie of the same name starring Stockard Channing and Will Smith.

Released to critical acclaim, the film represented an early version of the crowd-pleasing, everything-is-connected conceit that showed up a decade later in award-winning films like “Babel” and “Crash.”


Kevin Bacon in 2014. Mr. Bacon became the subject of a popular alternative to the six degrees of separation idea. Credit Richard Shotwell/Invision, via Associated Press

Many people were introduced to the theory through a slightly different version of the game, which uses any celebrity’s proximity to the actor Kevin Bacon on a cast list as a measure of how much weight he or she carries in Hollywood. In an interview with BuzzFeed in 2014, Mr. Bacon said he originally thought the game was “a joke at my expense,” but eventually came to peace with it and even named his charity SixDegrees.org.

But Mr. Karinthy’s theory has also been of interest to the social sciences. In 1967, the psychologist Stanley Milgram set up the “small world experiment,” a practical application of the idea of degrees of separation using hand-delivered packages. He confirmed the six degrees of separation, although his results were disputed.

More recently, the sociologist Duncan Watts imitated the “small world” experiment” through email, and found that Mr. Milgram’s results, though disputed, were “in the ballpark.”

Nicholas Christakis, the co-author of “Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives,” linked our fascination with recognizing strangers to a biological urge to distinguish friend from foe. He recalled the legends of medieval knights meeting on the road and stopping to recite their lineages.

“If they found that they shared a great-uncle or one of them had been a vassal to a similar king, they would dismount, hug each other and swear loyalty,” he said. “But if they found that they had no overlap, they would fight to the death.”


NYT > Technology

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