Partner Selection Shapes the Strategic and Topological Evolution of Cooperation

Coevolution of individual strategies and social ties, in which individuals not only adjust their strategies by social learning but also switch their adverse partners to search for potential beneficial ones, has attracted increasing attention very recently. It is found that the interplay of strategic updating and partner network adaptation can facilitate the escape from the stalemate of cooperation in social dilemmas. But the question how individual preferential partner choice shapes the dynamical and topological organization of cooperation has yet to be fully answered. Here we propose a simple evolutionary game model to address this problem. In our model, when severing a current disadvantageous partnership, individuals can choose a new partner, either among their friends of friends preferentially according to their reputation scores or randomly from the remaining population. In addition to partner switching, individuals also update their strategies by imitating social neighbors. The interplay between these two processes gives rise to rich evolutionary dynamics. We focus on both strategic and topological evolution. We find that reputation-based partner selection leads to highly heterogeneous and often disassortative partner networks. During the coevolutionary process, a few successful individuals who attain a large number of partners emerge as social hubs and thus directly influence periphery individuals of small degree, forming leader–follower hierarchical structures. Cooperation prevails because of the positive feedback effects: good guys attract more partnerships and “the rich get richer.” Our work sheds light on the emergence and maintenance of cooperation on dynamically changing social networks, where reputation plays a decisive role in the formation of social ties.