Figure 1.

The noisy iterated Prisoner's Dilemma game. Each round, players simultaneously decide if they will try to split or steal a pot of money but their choice may be imperfectly executed (e.g. Player A intends to split but steal is performed). Mechanisms for modelling the interaction between players can be distinguished by their inputs (e.g. do decisions to split only depend on features of the environment, do they depend only on the partners actions, do they depend on joint behaviours?) and whether they posit internal state such as beliefs about the partner or beliefs about the partner's beliefs. (Online version in colour.)