12 hours of Kevin Bacon: finding anyone in a social network


Crowdsourcing as a method of locating important people or information has become a familiar accompaniment to the aftermath of disasters. But are people really effective at locating a target, or do they just throw out blanket broadcasts? How quickly can people mobilize their social networks? The answers to these questions have become even more relevant with the fervor displayed on Reddit during the search for the Boston bombing suspects.

The small-world experiment that gave us the concept of six degrees of separation has a new counterpart in the internet age. The State Department’s Tag Challenge had teams search for five “thieves” (portrayed by actors, pictured below) in five international cities. The winning team, who found three of the five targets in less than 12 hours, have now released research analyzing their performance. They were interested in people’s mobilization efforts under time pressure, particularly whether messages were targeted (like @ mentions on Twitter) or whether social network participants engaged in a blind search.

In their Tag Challenge data, the researchers found that geographically targeted tweets increased over time, especially as the deadline approached. They think this represents conscious mobilization efforts as time became critical to the task, similar to the locally targeted geographic mobilization seen during Occupy Wall Street. They also found that successful mobilization requires passive participants. These are people who don’t sign up or recruit their friends into the challenge, but are aware of the efforts and pass on this information in other ways.


In a simulation of how people choose to use their social network to locate someone, the proportion of messages reaching the target cities was about 0.46, higher than what would be expected with a random flow of messages. The simulation was based on the constraints of the Tag Challenge, where the targets’ geographic locations (but not identities, save for a mugshot) were known, so real world situations might play out slightly differently.

The researchers think the fast discovery of people via social networking depends on thoughtful targeting. When people are being bombarded with news and social media, an @ mention may cause them to pay more attention, and a geographically targeted message may hit closer to home and give the recipient more of a reason to care. The recursive incentive scheme used by the winning team, which landed them 4,400 sign-ups within 48 hours, was also a crucial part of their success.

There is no doubt that the world has shrunk with online social networking. “We can find any person (who is not particularly hiding) in less than 12 hours,” wrote the study’s authors; their claim seems to be borne out by other research showing only four degrees of separation on Facebook. Correct identification may not be as easy in the real world, though, where “suspects” don’t wear t-shirts identifying them as targets, and the wisdom of the crowd can degenerate into frenzied fingerpointing.


Robert Ferguson

The world is shrinking, like bats with their antenna, all objects can be avoided if they have no relevance to a bat hunting for prey, If we have a large crowd and are looking for only a couple of objects (prey) (bombers) we remove all irrelevant data, til we are left with what we were shown , a couple of snaps of the bombers, as all others were seen as (irrelevant)

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