To promote the common good, should helpers be rewarded, or should free riders be punished? Although the bulk of previous research has fingered punishment as the best enforcer, a new study published online today in Science found that rewards are more effective.

"Groups that used rewards got significantly higher payoffs than groups that punished," David Rand, a lead study author and postdoctoral researcher at Harvard University's Program for Evolutionary Dynamics, said in a Science podcast.

He and his team used a classic public goods game to study how groups of volunteers encouraged the best outcome for the most people. In a series of monetary interactions, individuals decided how much money to contribute to a common pot, and they could then decide whether to reward good contributors or punish bad—both of which would entail spending money.

Previous public goods studies had focused on one-time interactions and found that people were more likely to swindle or punish others. But in situations where interactions were repeated, people found greater success in reward-based structures—in which those that contributed were rewarded and those who didn't were ignored—than those in which costly punishment was doled out to those who didn't contribute.

Rand explained in the podcast that the findings also have straightforward applications in everyday life. "Our studies suggest that you would do well to be nice to the people that are helpful to you, or be nice to the people who you see contributing to the group, and you see people sort of not doing their part—as opposed to sort of going out of your way to really hurt them and punish them for it, you should just stop helping them, and use denial of reward as an incentive for them to do their part," he said. 

The authors of the study distill the lesson to next-door-neighbor relations: "If I resent my neighbor's gas-guzzling SUV, I could exercise costly punishment by slashing his tires," which "carries the risk of retaliation," they write. "Conversely, I could be extra helpful to my other neighbor who just bought a low-emission vehicle."

Just how these findings translate beyond the home and office into a broader, more codified legal context needs further examination. "It's unclear to what extent these results generalize to politics," said Rand in the podcast. But he and his team are looking into this question of whether standardizing a reward or punishment for a specific action will change the decisions in public goods games. 

Other similar games across the globe have found some cultures where punishment is doled out to high contributors rather than low contributors, a dynamic that Rand singles out as particularly harmful to the overall public good. "Punishment can be really destructive when the low contributors punish the cooperators," he said. "But with rewards, there's no such danger of that because if you have people rewarding each other when they shouldn't that's good, really."

Image of the study authors courtesy of David Rand