Cooperation in Society: How Our Memory Influences Our Behavior

December 09, 2024

Cooperation often arises through "direct reciprocity," meaning we help others because we expect them to help us in return. A new study conducted by scientists from the Max Planck Institute for Evolutionary Biology, the City College of New York, and Harvard University investigates how memory and strategy complexity influence cooperative behavior. The researchers found that strategies that consider not only the last move of a co-player but also previous moves lead to higher cooperation. It is particularly important to analyze the full behavior of the co-player, rather than merely counting how often they have cooperated in the past. These findings highlight that longer memory and more complex, context-based strategies are necessary to promote long-term, fair cooperation.

In many social interactions, people operate based on the principle of "direct reciprocity": Blue helps Red because Blue expects to receive help from Red in the future. Models of repeated games have significantly advanced our understanding of the mechanisms behind direct reciprocity. In each round of a repeated game, two players independently decide whether to cooperate (C) or defect (D). Traditionally, repeated game models assume that players base their decisions solely on the most recent interaction. But what happens when decisions take into account a longer history of past interactions?

© Nikoleta E. Glynatsi

In many social interactions, people operate based on the principle of "direct reciprocity": Blue helps Red because Blue expects to receive help from Red in the future. Models of repeated games have significantly advanced our understanding of the mechanisms behind direct reciprocity. In each round of a repeated game, two players independently decide whether to cooperate (C) or defect (D). Traditionally, repeated game models assume that players base their decisions solely on the most recent interaction. But what happens when decisions take into account a longer history of past interactions?

© Nikoleta E. Glynatsi

The ability to cooperate plays a crucial role in many areas of human life—whether in the workplace, in politics, or in personal relationships. A new finding shows how memory and the recollection of past behavior can influence the willingness to cooperate. This insight is particularly relevant for shaping social and economic systems where trust and cooperation are central.

In many social interactions, we operate based on the principle of "direct reciprocity"—we help others because we expect them to help us when we need it. Traditionally, cooperation has been explained using simple strategies that only consider the most recent behavior. These so-called memory-1 strategies, which only consider the last action of a co-player, have long dominated scientific research. However, in real-world social situations—such as in workgroups, among politicians, or in interpersonal relationships—past actions often also play a role. Especially in complex and error-prone environments, people tend to rely on more "memory" to make decisions.

The recent study conducted in this context explores how longer-term memory in social interactions can lead to better cooperation. The researchers focused on so-called "reactive-n strategies," which are based on the co-player’s actions over several previous rounds. They found that strategies that take more past behavior into account can stabilize cooperation and promote it in the long term. These results have important implications for our understanding of cooperation in society: they show that a long-term perspective on others' behavior—the "memory" of past cooperation or conflicts—can enable stable collaboration.

These findings are especially important in dynamic social environments, where mistakes and misunderstandings frequently occur. They explain why, in groups where long-term relationships matter (such as in teams or political partnerships), the willingness to cooperate increases when the entire history of collaboration is considered. For businesses and organizations, this might mean fostering a culture of trust and long-term collaboration, where mistakes do not immediately lead to the breakdown of cooperation.

Overall, the latest findings show that memory plays a key role in promoting cooperation—not only in theoretical models but also in everyday life and the design of social systems. They offer a new perspective on how long-term collaboration can be successfully structured in a world often shaped by short-term interests and mistakes.