Figure 1. Dynamics of social ties: In a sample configuration a focal individual i considers severing its link to a randomly selected beneficiary m and establishing a new link to a randomly chosen member of the population n, who is not already a beneficiary of i's help.

The colour shades indicate the behavioural type of the individuals along with their payoffs (white) prior to any changes to i's links. (a) The beneficiary m is an egoist (red) and more successful than the altruistic focal individual i (blue). Because m is also less cooperative than i, the focal individual is likely to withdraw its help in an attempt to mimic the strategy (fewer outgoing links) of a more successful individual. (b) The individual n is a fair player (green) and more successful. Because n is also more cooperative than i, the focal individual is likely to establish this new link and provide benefits to n, again attempting to mimic the strategy (more outgoing links) of more successful individuals. Benefits can return to the actor either through (I) directed loops (indirect reciprocity) or (II) bi-directional links (direct reciprocity).