New Study by IT:U Professor & Co Reveals Stable Strategies for Cooperation in Social Dilemmas
Why do people sometimes withhold effort in group projects, overexploit public goods, or fail to coordinate even when mutual success is possible? These are all examples of social dilemmas—situations where what’s best for an individual may not align with the group’s interests. A new study by Valentin Hübner, Laura Schmid, Krishnendu Chatterjee, and Christian Hilbe— IT:U professor of the Game Theory and Evolutionary Dynamics research group—tackles these dilemmas head-on.
What’s the Big Idea?
In social dilemmas, two main forces guide cooperation: direct reciprocity, where people help those who have helped them, and indirect reciprocity, where decisions are based on someone’s reputation. Although both kinds of reciprocity often influence real-world decisions together, most academic research has focused on them in isolation—until now.
In this new study, the researchers introduce a general framework that combines direct and indirect reciprocity to cover all social dilemmas, not just simplified cases like the “donation game.” And their results are surprising:
Cooperation can always be sustained as a Nash equilibrium—a stable outcome where no one has an incentive to defect—no matter:
- Whether individuals rely on personal experience or public reputation
- Whether the game is repeated indefinitely or ends randomly
- Whether everyone agrees on each other’s behavior or not
In short: cooperation isn’t just possible—it’s robust.
Why It Matters
The study shows that human cooperation is not fragile. Even in chaotic or uncertain environments, people can find ways to work together—if the right strategies are in place.
Some real-life relevance includes:
- Human Behavior: It supports how cooperation can evolve and survive in real-world communities, even with imperfect information.
- Social Systems: Helps explain why people still contribute to shared goals—like public goods or collective decisions—even when things get messy.
- Incentive Design: Offers guidance for building better rules in teams, online platforms, or negotiations, where repeated interactions matter.
“This kind of research is crucial to explore how people use information about others to make social decisions. One particularly interesting question arises when there are conflicting pieces of information. For example, can I trust friends that have a poor public reputation, even though have always been cooperative in any direct interactions? To address such questions, it takes an interdisciplinary approach, combining methods and insights from social psychology, mathematical modeling and computer simulations.”
— Christian Hilbe, IT:U Professor for Game Theory and Evolutionary Dynamics
Meet the Interdisciplinary Team
- Valentin Hübner – Institute of Science and Technology Austria (ISTA)
- Laura Schmid – Kim Jaechul Graduate School of AI, Korea Advanced Institute of Science and Technology (KAIST)
- Krishnendu Chatterjee – Institute of Science and Technology Austria (ISTA)
- Christian Hilbe – Interdisciplinary Transformation University Austria (IT:U Austria)
Together, their cross-institutional collaboration proves that bridging disciplines and perspectives—just like direct and indirect reciprocity—leads to stronger outcomes.
Read the full paper and key findings:
“Stable strategies of direct and indirect reciprocity across all social dilemmas”
Published in PNAS Nexus (May 2025)
👉 https://doi.org/10.1093/pnasnexus/pgaf154