Figure 1.

Two monitoring systems in indirect reciprocity. (a) Private monitoring: each potential observer can observe a game independently with the probability, q, and otherwise cannot. The actual observers privately assess a donor of the game and the non-observers never update their assessments of the donor. (b) Public monitoring: a representative device observes a game and delivers its public assessment of a donor in the game to all of players with the probability, q; otherwise, the device does not observe the game and the assessment of any player is never updated.