Figure 5
From: Reputation structure in indirect reciprocity under noisy and private assessment
An interpretation of the equilibrium state for SS. (A) When a donor cooperates with a recipient, the donor receives good reputations from a lot of observers, independent of classes of the donor and the recipient. Such a donor moves to class-1. Because this process frequently occurs, SS generates a majority of individuals with high goodness. (B) When a donor defects with a recipient in class-1, the donor receives bad reputations from a lot of observers and such a donor moves to class-2. This process does not frequently occur, but SS definitely generates a minority of individuals with low goodness.
