Trusting behavior in prisoner's dilemma: The effects of social networks

The prisoner's dilemma (PD) game has been studied to understand how social order is formed between two persons. The study of social dilemmas extends the relation from two persons to N persons. However, in these studies, experiments are normally executed using subjects who do not have previous contacts. The intention of these studies is to show how a cooperative state is achieved. In contrast, this study is intended to show how people change or maintain the social order after they formed a group. This study demonstrates how members of existing groups think and behave in anonymous one-shot PD game.; The key concept is trust among the members of the group. Trust (especially personal trust), defined as the expectation of positive reward from particular others, is important in this context. It is natural that in existing groups, not all the members trust one another. There may be some people who distrust each other. Nevertheless, they seem to maintain their social order well in the groups. Why? It suggests that there may be a mechanism that encourages people to place trust in others.; In fact, we find that subjects' thoughts and behaviors are influenced by the trust structure of the group. This study concerns specifically the structure of symmetry and transitivity of trust. The main finding is that subjects become more cooperative as the transitivity of trust relation in the group becomes higher, but subjects are not influenced by the symmetry of the group. That is, people in the group cognitively count on trust relations among others when they behave.; The implication of this study is that the social order as a cooperative state can be achieved by formation of transitive relations within groups. Theoretically, this suggests that instead of constructing a costly sanction system in the group, naturally formed transitivity plays a role to maintain a mildly cooperative group. Unless very strict cooperation is required, transitivity formation may be sufficient to maintain the order within groups.