SAN JOSE, Calif. — Yahoo Inc. and Facebook Inc. are
joining forces to test an iconic 1960s-era social experiment that showed
there are just six degrees of separation between most people on the
The world’s population has almost doubled since
social psychologist Stanley Milgram’s famous but flawed “Small World”
experiment gave people a new way to visualize their interconnectedness
with the rest of humanity. Something else has also changed — the advent
of online social networks, particularly Facebook’s 750 million members,
and that’s what researchers plan to use.
Starting this week, social scientists from Facebook
and Yahoo are hooking into that vast digital network to discover how
many average online connections it takes for people to relay a message
to a “target” — someone they don’t know, in countries around the world.
The Yahoo-Facebook experiment could settle ongoing
questions about whether the degrees of separation between people are as
few as Milgram and other investigators concluded. Milgram’s conclusion
was based on a small number of letters making it to their target,
leaving room for doubt about his findings among many social scientists.
The latest version of the Small World experiment running on Facebook
could help erase those questions.
“You really couldn’t have done this until very
recently,” said Duncan Watts, Yahoo’s principal research scientist who
is leading the experiment. “It’s a milestone, in terms of it’s the kind
of research question you can answer now that you could have imagined 50
years ago, but that you couldn’t have answered 50 years ago — or even 15
On average, each of Facebook’s members has 130
friends on the social network, and Facebook visualizes that web of
connections as a person’s “social graph.” The social graph doesn’t just
grow wider as the social network — Facebook has tripled in size in the
past two years — adds members. It also gets more dense, as the gaps
between people are filled in by new members, said Cameron Marlow,
Facebook’s chief data scientist.
While the digital record of that graph shows the
far-flung web of connections between people, individuals might not
always be aware of how large their network really is, because they don’t
always know the friends of their friends. Therefore, it’s important to
test how effective people really are at transmitting a message from
friend to friend, Watts said, to gauge how closely connected people
The current “Small World” experiment — anyone with a
Facebook account can participate by going to
smallworld.sandbox.yahoo.com — could help determine that. The study is
intended as academic social research and will be published in
peer-reviewed scientific journal, said Watts, a widely recognized
authority on social networks.
But the results could have applications to Facebook’s
business, Marlow said, because the degrees of separation between
individuals, and between people and commercial brands that run ads on
Facebook, are important. “Facebook depends on its connectedness, and the
fact that users are connected to each other and users are connected to
brands, enables the diffusion of important messages, a big part of which
is our advertising platform,” Marlow said.
The world had about 3.5 billion people when Milgram
conducted his “Small World” experiments in the 1960s. Milgram asked
groups of people in Wichita, Kan., and Omaha, Neb., to use their social
connections to get a chain letter to a stockbroker in Boston in as few
steps as possible.
The letters arrived in an average of 5.5 steps.
Milgram never used the “six degrees of separation” phrase, but it has
become a cultural icon.
Milgram “introduced the concept, or at least he gets
credit for it, that our social networks are all intertwined, so in fact
all of us are connected to other people through very few hops,” said
Santa Clara University psychology professor Jerry Burger.
It is now widely accepted that there were potential
flaws in Milgram’s research, said Phil Cowan, a professor emeritus of
psychology at the University of California-Berkeley, because his
conclusions were based on the small number of results — just 64 out of
the 300 letters Milgram sent made it to their target.
“Here you had a very surprising factoid, cloaked in
science, and I just think everybody who heard it, including me at the
time, said, ‘Wow, that’s amazing. We are more connected than we thought
we were,’ ” Cowan said. He said the validity of the current
Yahoo-Facebook study would depend on whether it’s representative of the
general population, particularly since social network users skew
Yahoo and Facebook hope to attract many times more
participants than Milgram could get through the U.S. mail, perhaps tens
or even hundreds of thousands. People who sign up see a thumbnail
description of their target, and then choose one person from their
Facebook friends who they think has the best chance of getting a step
closer to the target.
“This is our best chance to measure this fundamental
piece of the social graph, so the more users that participate, the
clearer the signal will be,” Marlow said.
Watts has already researched the small-world concept,
having published the first mathematical model of people’s social
connections in 1998 with a colleague at Cornell University. Five years
later as a professor at Columbia University, Watts used email to explore
the length of connections between people, and got similar results to
But he said Facebook’s network provides a much better proxy for the world’s 6.8 billion people.
“It’s not 6 billion, but it’s twice the size of the
U.S. population. If it works on this network, (the six degrees
hypothosis) really is true,” Watts said. “I don’t think anyone can say,
‘Oh, it works on Facebook, but it really doesn’t count.’ This is an
opportunity to show that it’s true, or not true.”
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