Investigating the Impact of Direct Punishment on the Emergence of Cooperation in Multi-Agent Reinforcement Learning Systems

Solving the problem of cooperation is of fundamental importance to the creation and maintenance of functional societies, with examples of cooperative dilemmas ranging from navigating busy road junctions to negotiating carbon reduction treaties. As the use of AI becomes more pervasive throughout society, the need for socially intelligent agents that are able to navigate these complex cooperative dilemmas is becoming increasingly evident. In the natural world, direct punishment is an ubiquitous social mechanism that has been shown to benefit the emergence of cooperation within populations. However no prior work has investigated its impact on the development of cooperation within populations of artificial learning agents experiencing social dilemmas. Additionally, within natural populations the use of any form of punishment is strongly coupled with the related social mechanisms of partner selection and reputation. However, no previous work has considered the impact of combining multiple social mechanisms on the emergence of cooperation in multi-agent systems. Therefore, in this paper we present a comprehensive analysis of the behaviours and learning dynamics associated with direct punishment in multi-agent reinforcement learning systems and how it compares to third-party punishment, when both are combined with the related social mechanisms of partner selection and reputation. We provide an extensive and systematic evaluation of the impact of these key mechanisms on the dynamics of the strategies learned by agents. Finally, we discuss the implications of the use of these mechanisms on the design of cooperative AI systems.