Cooperation in the Prisoner's Dilemma with Anonymous Random Matching

TLDR

The study examines repeated prisoner's dilemma games in large populations with anonymous random matching, where players cannot identify opponents. The authors aim to extend the analysis to settings with heterogeneous time preferences and without public randomizations. They find that even without opponent recognition, cooperation can arise as a sequential equilibrium via contagious punishments, requiring only moderate patience, being robust to noise, and achieving near‑efficiency.

Abstract

The paper considers the repeated prisoner's dilemma in a large-population random-matching setting where players are unable to recognize their opponents. Despite the informational restrictions cooperation is still a sequential equilibrium supported by "contagious" punishments. The equilibrium does not require excessive patience, and contrary to previous thought, need not be extraordinarily fragile. It is robust to the introduction of small amounts of noise and remains nearly efficient. Extensions are discussed to models with heterogeneous rates of time preference and without public randomizations.