Comparison between different models.

Comparison between observation probabilities in different models of indirect reciprocity. is the probability that the donor knows the recipient's reputation. is the probability that the observer knows the recipient's reputation and uses it to assign a reputation to the donor. is the probability that the observer observes the donor's action and assigns a reputation to the donor. In most previous models, has been assumed to be real valued, whereas is binary, i.e., or . In our model, is also real valued such that observers as well as interacting players of the game have incomplete information about the recipient's reputation.