Trust and cooperation: a new experimental approach.

Several theories within different disciplines emphasize the role of trust in fostering cooperation in human social life. Despite differences, the core of these notions of trust is affectively motivated loyalty, which makes the individuals feel mutually committed and willing to accept vulnerability because of positive expectations about each other's behavior. In evolutionary game theory and experimental economics, the notion of trust is much simpler: it is an expectation about another's behavior, a kind of wager, in which the sense of mutual commitment and vulnerability is completely absent. In order to extend the paradigm of trust games typical in those fields to explore the fuller sense of trust relationships, we have developed a new experimental design, in which an iterated prisoner dilemma is played by participants who do or do not hold a trusting personal relationship, while anonymity is preserved. We present here the results of our two pilot studies, which indicate the relevance of personal trust in fostering cooperation and suggest the influence of the structure of social networks on the degree of cooperation achieved.