Indirect reciprocity theory holds that people who earn a good reputation by helping others are more likely to be rewarded by third parties, but widespread cooperation depends on agreement on reputation. In most theoretical models that examine how reputations impact people’s desire to cooperate with each other, reputations are binary (good or bad) and based on limited information. But there is a lot of information available about people’s behavior in today’s world, especially on social media.
Biology professors Joshua B. Plotkin of the University of Pennsylvania and Corina Tarnita of Princeton University lead teams that have been collaborating on theoretical research on cooperation. Sebastián Michel-Mata, a PhD student in Tarnita’s lab, came up with the idea of addressing how to judge someone in an information-rich environment.
“Current theory of indirect reciprocity suggests that reputations can only work in a few societies, those with complex norms of judgment and public institutions that can enforce agreements,” says Michel-Mata. But as an anthropologist, he sees that such societies are the exception rather than the rule, and he questions the simple idea that reputations are summaries of multiple actions.
“Previous models have generally assumed that a single action determines someone’s reputation, but I think there is more nuance to how we assign reputations to people. We often look at multiple actions someone has taken and see if they are mostly good or bad actions.” says Mari Kawakatsu, a postdoctoral researcher in Plotkin’s lab.
Through mathematical modeling, the research team showed that observing multiple actions and forgiving some bad actions is a method of judging behavior sufficient to maintain cooperation, a method they call “look twice, forgive once.” Their findings are published in Nature.
This builds on earlier work that Plotkin conducted on indirect reciprocity. For example, he worked with Kawakatsu and postdoctoral researcher Taylor A. Kessinger on a paper that estimates how much gossip is necessary to reach enough consensus to sustain cooperation.
Plotkin says of the new paper: “Even if different people in a society subscribe to different standards of judgment, ‘look twice, forgive once’ still generates enough consensus to promote cooperation.” He adds that this method maintains cooperation without gossip or public institutions, confirming the original hypothesis of Michel-Mata, first author of the article, that public institutions are not a prerequisite for reputation-based cooperation. It also offers an important alternative when public institutions exist but the erosion of trust in the institutions inhibits cooperation.
Kessinger says that, as in the gossip article, the game theory model here is a one-time donation game, also known as a simplified prisoner’s dilemma. Each player can choose to help or not help their partner, and players will periodically update their views on each other’s reputations by observing each other’s interactions with each other. other players, to see if the partner cooperates or “defects” to others. More periodically, players update their strategies.
The idea of indirect reciprocity “isn’t that I’m nice to Mari because she was nice to me; it’s that I’m nice to Mari because she was nice to Josh, and I think highly of Josh,” Kessinger says. In this study, “the basic idea is that if you observe two interactions of someone and at least one of them is an action that you consider good, then you cooperate with that player, but otherwise you defect to him.”
Kawakatsu says that all the co-authors were surprised that the “look twice, forgive once” strategy could not be replaced by other strategies, such as always cooperating or always defecting, observing more than two actions of another player, or forgiving in a proportion different. of “bad actions.” Tarnita says that, perhaps most surprisingly, looking more than twice produced no additional benefit. “Information turned out to be a double-edged sword, so that even when information was freely accessible, individuals did not evolve to fully utilize it,” he says.
Michel-Mata notes that the simplicity and overall robustness of their findings indicate that this behavioral strategy could be ancient in human societies. The authors see potential for anthropologists and behavioral scientists to build on their work.
The Plotkin and Tarnita labs continue to collaborate exploring how people interact in more than one context, such as at work and in their personal lives. “This touches on a number of contemporary social problems,” says Kessinger, “where private misconduct becomes a matter of public record.”