Updates in Cooperative AI

Indirect reciprocity is a key mechanism for sustaining cooperation in mixed-motive settings. By helping someone, agents can enhance their reputation, increasing the chances that others reciprocate and cooperate back with them in the future. The reputation of individuals depends, in turn, on social norms that define a good or bad action, offering a mathematically appealing way of studying the emergence of moral systems. In this presentation, Fernando will introduce indirect reciprocity models with increasing complexity. First, a model based on evolutionary game theory, to understand cooperation dynamics under different social norms. Second, a model of (independent) reinforcement learning, where agents belong to multiple groups and might learn to reciprocate exclusively with their own group. Third, he will discuss the effects of having reputations assigned by LLM-based agents. He will show that indirect reciprocity norms revealed by LLMs exhibit high variance, within and between models, which significantly impacts the dynamics and prevalence of cooperation.
We’re delighted to host this ninth seminar in our 'Updates in Cooperative AI' series. You're welcome to subscribe to our Google Calendar to stay up-to-date on all upcoming events.
Speakers

Fernando Santos (Informatics Institute, University of Amsterdam)

Discussants
Time

16:00-17:00 UTC 29 July 2026

Links
This seminar has now finished
Register Here

Fernando Santos is an Associate Professor at the Informatics Institute of the University of Amsterdam. He is part of the SIAS group, where he leads the Prosocial Dynamics Lab. His research lies at the interface of AI and Complex Systems: he studies behavioural dynamics in systems of adaptive learning agents and aims at designing prosocial and fair AI. Previously, he was a James S. McDonnell Postdoctoral Fellow at Princeton University. He completed his PhD in Computer Science and Engineering at Instituto Superior Técnico (University of Lisbon). Fernando is an ELLIS Scholar and ERC Starting Grant recipient. His work received the Victor Lesser Dissertation Award at AAMAS and the APPIA Best AI Thesis in Portugal.

Cooperation Through Reputation in Multi-Agent Systems