通过数值模拟，我们还发现网络间的链接对大规模相互依存网络中的合作行为传播至关重要。适当的网络间链接能够最大程度的促进合作。原因在于，具有网络间链接的节点更倾向于选择合作策略，如图。

邻近节点为合作者的数目与个体选择合作策略概率的关系。

Spreading of cooperative behaviour across interdependent groups

Recent empirical research has shown that links betweengroups reinforce individuals within groups to adopt cooperative behaviour.Moreover, links between networks may induce cascading failures, competitive percolation,or contribute to efficient transportation. Here we show that there in factexists an intermediate fraction of links between groups that is optimal for theevolution of cooperation in the prisoner’s dilemma game. We consider individualgroups with regular, random, and scale-free topology, and study their differentcombinations to reveal that an intermediate interdependence optimallyfacilitates the spreading of cooperative behaviour between groups. Excessivebetween-group links simply unify the two groups and make them act as one, whiletoo rare between-group links preclude a useful information flow between the twogroups. Interestingly, we find that between group links are more likely toconnect two cooperators than ingroup links, thus supporting the conclusionthat they are of paramount importance.

论文链接：

http://www.nature.com/srep/2013/130821/srep02483/full/srep02483.html

论文下载：

Spreading of cooperative behaviour across interdependent groups.pdf