Digital bounty hunters unleashed

Online pay strategy quickly coordinates cross-country balloon posse

These days, bounty hunters aren’t deputized, they’re digitized: Online crowd-sourcing strategies to induce masses of people to solve a task, such as locating far-flung items or alleviating world hunger, work best when financial incentives impel participants to enlist friends and acquaintances in the effort, a new study concludes.

In a competition to find 10 red weather balloons placed across the United States, a team of MIT researchers used online social media and a simple reward system to recruit balloon-searchers in the 36 hours preceding the contest. Their pay-based strategy garnered them 4,400 volunteers who located all the balloons in a contest-winning eight hours, 52 minutes.

“Our incentive system offers monetary rewards, but perhaps more importantly it builds social capital between you and the people you recruit, who get an opportunity to participate in something interesting,” says MIT computer scientist Alex Pentland. This strategy could boost the effectiveness of humanitarian and marketing campaigns, Pentland and colleagues conclude in the Oct. 28 Science.

Many digital crowdsourcing strategies have recently appeared. Paying people works for some tasks, as the MIT team found, but other tasks hinge on self-motivation that may get undermined by promises of money, says computer scientist Matthew Lease of the University of Texas at Austin. Wikipedia, for instance, parlays individuals’ inherent interests and specialized knowledge into collective encyclopedia entries.

Other crowdsourcing incentives include creating opportunities for people to socialize with others, to gain public recognition and to contribute to a valued cause, Lease says.

The goal of the 2009 balloon-hunting contest was to explore digital strategies for rapidly mobilizing people into intelligence-gathering networks. More than 50 groups entered the competition, which was sponsored by DARPA, the Pentagon’s Defense Advanced Research Projects Agency.

Only MIT’s team found all 10 balloons. To get the recruiting ball rolling, the researchers sent a link for the team’s website to a few friends and several bloggers about 36 hours before the contest began.

Portions of the $40,000 winner’s prize were promised to everyone who contributed to the search. A maximum of $4,000 was allocated to finders of each balloon — $2,000 to the first person to send in the correct balloon location, $1,000 to the person who invited the balloon finder onto the team, $500 to whomever recruited the inviter, and so on.

Participants received about $33,000 for their efforts.

The number of Twitter messages mentioning the MIT team rose substantially the day before the contest and remained elevated until the competition ended, a sign that the reward strategy worked, Pentland says.

Second-place finishers from the Georgia Institute of Technology recruited 1,400 participants by offering to donate winnings to the American Red Cross. They located nine balloons in nine hours. Their strategy sparked a brief rise in team-related tweets that faded before the contest started, suggesting that do-good appeals didn’t mobilize volunteers as much as pay incentives did.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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