The U.S. Defense Advanced Research Projects Agency's (DARPA) Network Challenge earlier this month demonstrated that social networks, more than being platforms for self-promotion, can be also be highly effective tools for rapidly gathering and disseminating very precise information. With the help of Facebook, Twitter and a homemade Web site, a winning team from the Massachusetts Institute of Technology (M.I.T.) was able to within nine hours identify the correct latitude and longitude of all 10 of DARPA's red weather balloons, which were lofted 30.5 meters into the air at locations scattered throughout the U.S.
The competition was instructive not only in the ways that social networks can be successful at crowd-sourcing—using the Internet's long reach to rally disparate groups of people together for a common cause—but also in revealing different ways people can be motivated to participate. Whereas the M.I.T. Media Lab's Red Balloon Challenge Team's approach was to promise a share of the $40,000 in prize money to those that helped them win, the Georgia Tech Research Institute (GTRI) "I Spy a Red Balloon" team in Atlanta (which placed second out of 58 teams) located nine of the balloons in nearly the same amount of time as M.I.T. with the promise of donating all of their winnings to the American Red Cross.
The M.I.T. researchers jumped at the opportunity to participate in a competition that would allow them to further their Human Dynamics Laboratory studies of how people interact with technology. Almost from the outset the team decided on a "temporary recursive incentive" model that would reward not just the balloon finders but also the network of people responsible for putting the team in touch with the balloon finders, says Wei Pan, a first-year M.I.T. Media Lab graduate student and member of the winning team.
The Red Balloon Challenge Team offered $4,000 in reward money per balloon. This included $2,000 per balloon to the first person to send them the correct coordinates and $1,000 to the person who invited the balloon finder to join M.I.T.'s balloon-finding network. If there were a third person in the network chain (the person who invited the inviter to join), that person would receive $500. Whoever referred the $500 winner to the team would be entitled to $250, and so on. The team—which included students Pan, Manuel Cebrian, Anmol Madan, Galen Pickard and Riley Crane as well as Human Dynamics Laboratory director Sandy Pentland—decided any leftover money would go to charity.
"We wanted to understand how Facebook, Twitter and other social networks have changed the way humans mobilize," Pan says. "We also wanted to see how, with minimal cost to us, we could harness the powerful resources offered by the online community." The balloons ended up being widely dispersed throughout the U.S., in cities including Memphis, Miami and San Francisco as well as smaller venues such as Christiana, Del., and Katy, Tex.
The GTRI team considered paying for reported information about the balloons' locations but opted against it. "We figured we could get our network more widespread if we appealed to them by supporting a charity," says Erica Briscoe, a GTRI research scientist. The team carefully considered charities, ultimately choosing the American Red Cross. "We were looking for something nonreligious and noncontroversial," says GTRI research engineer Ethan Trewhitt. "We didn't want anyone using the charity as a reason for not joining."