An experiment examined whether and how the relationship between individual differences in social attachment and cooperation is modulated by brain oxytocin, a neuropeptide implicated both in parent-child bonding, and in social approach. Healthy males completed a validated attachment style measure, received intranasal oxytocin or placebo, and privately chose between cooperation and non-cooperatio...

Why cooperation is well developed in human society is an unsolved question in biological and human sciences. Vast studies in game theory have revealed that in non-cooperative games selfish behavior generally dominates over cooperation and cooperation can be evolved only under very limited conditions. These studies ask the origin of cooperation; whether cooperation can evolve in a group of selfi...

Throughout their life, humans often engage in public goods games in situations ranging from family related issues to global warming. In all cases, the tragedy of the commons threatens the possibility of reaching the optimal solution associated with global cooperation. Up to now, individuals have been treated as equivalent in all respects, in sharp contrast with real life situations, where diver...

Throughout their life, humans often engage in public goods games in situations ranging from family related issues to global warming. In all cases, the tragedy of the commons threatens the possibility of reaching the optimal solution associated with global cooperation. Up to now, individuals have been treated as equivalent in all respects, in sharp contrast with real life situations, where diver...

We study the emergence of cooperation in dynamic, anonymous social networks, such as in online communities. We examine prisoner’s dilemma played under a social matching protocol, where individuals form random links to partners with whom they can interact. Cooperation results in mutual benefits, whereas defection results in a high short-term gain. Moreover, an agent that defects can escape recip...

Using the theory and methods of non-linear dynamics, I explore the consequences of cooperation on the size and dynamics of social groups. I present a model that incorporates into a discrete growth equation a positive density-dependent factor to represent the synergistic effects of cooperation. Analysis of this model shows that, by increasing the net reproductive output of group-living organisms...

The evolution of cooperation described in terms of simple two-person interactions has received considerable attention in recent years, where several key results were obtained. Among those, it is now well established that the web of social interaction networks promotes the emergence of cooperation when modeled in terms of symmetric two-person games. Up until now, however, the impacts of the hete...

Cooperation among unrelated individuals is frequently observed in social groups when their members combine efforts and resources to obtain a shared benefit that is unachievable by an individual alone. However, understanding why cooperation arises despite the natural tendency of individuals toward selfish behavior is still an open problem and represents one of the most fascinating challenges in ...

Social networks with positive and negative links often split into two antagonistic factions. Examples of such a split abound: revolutionaries versus an old regime, Republicans versus Democrats, Axis versus Allies during the second world war, or the Western versus the Eastern bloc during the Cold War. Although this structure, known as social balance, is well understood, it is not clear how such ...

We analyze a novel agent-based model of a social network in which agents make contributions to others conditional upon the social distance, which we measure in terms of the “degrees of separation” between the two players. On the basis of a simple imitation model, the emerging strategy profile is characterized by high levels of cooperation with those who are directly connected to the agent and l...