Evolutionary dynamics of reciprocity and the evolution of cooperation [MCB]
Humans readily cooperate in large groups of strangers. This is hard to explain from an evolutionary perspective, since the evolution of cooperation often relies on kinship. One way out of this conundrum is the idea of reciprocity. Cooperation can be promoted by allowing agents to condition their behaviour on reputation, in what is known as indirect reciprocity. If I help you, somebody else will help me. Social norms - dictating how agents update the reputations of others - are central in determining whether this mechanism is effective in promoting cooperation. In particular, norms that reward justified defection have been shown to promote cooperation. A major limitation of existing models is that they assume all agents adopt the same norm. We present a model where agents can choose both how to react to reputations and how to assign the reputations of others -- making social norms emergent. We find that when agents can spontaneously adopt novel norms, a finite population will drift towards uncooperative behaviour.
We compare the emergent dynamics with models of direct reciprocity (I help you and you help me); concluding that reciprocity alone (direct or indirect) is ineffective in promoting cooperation. I discuss what modern models for the evolution of human cooperation may look like, aiming to falsify competing hypothesis and embracing stylised facts of human sociality.
Dr Julian Garcia, Monash University