Cooperation through communication: Agent-based models and experimental results

In human societies, reputation is a complex artefact. It relies on the tendency of group members to assess one another and its ultimate function is to perform distributed social control, i.e. the enforcement of social accepted norms and behaviours without the presence of a centralised institutional actor. This goal is accomplished by means of evaluations spreading (gossip) among the members of the same group. Hence, reputation is described as an information transmission process. The inputs of the process are the beliefs that group members autonomously acquire during social interactions, while its output is an emergent property for the evaluated agent, i.e. what an agent is believed to be (according to given social norms) as a result of the spreading of evaluations about him/her. Since social actors interact in a non-linear way, Agent-Based Social Simulation (ABSS) is a candidate methodology for the study of gossip and reputation. By means of computer models, ABSS allows the design of the behaviour of artificial entities ---the agents--- and the local rules that govern their interactions. The simulated dynamic, then, allows to observe the properties that emerge at the level of the systems, which can be statistically analysed. Simulations were implemented in scenarios that represent different forms of strategic interactions, allowing us to test how and to what extent circulation of information influence cooperative behavior. Two forms of communication mechanisms were tested: one with private information, the other with public information. Moreover, an additional case scenario is analysed: an Industrial district populated by artificial firms. Industrial districts (Ids) can be conceived as complex systems made of heterogeneous but strictly interrelated and complementary firms. One of the distinctive features of industrial districts is the tight connection existing between the social community and the firms: in this context, economic exchanges are mainly informed by social relationships and holding good reputation is an asset that may actually foster potential relations. In this work we modelled the effects of two kinds of social evaluations: namely Image (direct evaluations) and Reputation (reported evaluation). Likewise, we compared the effects of sincere and insincere information on the economic performances of the single firms and of the cluster as a whole. In a different experimental settings ---performed with groups of natural subjects interacting through a graphic computer interface--- we analysed reciprocal forms of messages exchanges. The positive effects of communication on rates of cooperation is a robust experimental finding. When individuals can talk to one other, cooperation increases significantly. Proposed explanations to this phenomenon consider the formation of group identity, as well as the chance to make explicit commitments ---where reputational and moral factors come into play--- as fundamental causes. This research, however, looks at communication as a mean to establishing and enforcing cooperation among people; to our knowledge, no attempt has been made to analyze communication strategies, when communication processes are actually the place where cooperation evolve. We developed a novel experimental setting in which participants playing a memory game (with numbers instead of images) could either play alone, or exchange messages containing the position and the value of the cards, so that those who received a truthful message could more easily get a match. This setting was conceptually modeled after the stag hunt game, a coordination game in which players do better if they coordinate their behavior with the behavior of others. In our experiment, playing alone is faster than sending messages, but it leads to a quicker depletion of the available moves. On the contrary, sending messages is more time consuming, but it allows players to know the position of cards, provided the information is correct, without wasting moves in trying to guess. Results show that the exchange of messages is a mutually beneficial activity, allowing participants to jointly discover the game board, to score higher and more efficiently. Cooperation through communication is conditional to receiving messages from other participants and is performed with this very expectation (as reported by the majority of the subjects afterwards). This strategic behavior could be explained according to two alternative frameworks: either a game-theoretical interpretation of reciprocity, analyzed as an imitation strategy (Tit-For-Tat); or a cognitive view in which cooperative behavior is regarded as a socially prescribed activity, and every deviation from the norm is punished according to the interpretation of the violation. The absence of retaliatory behaviour; and a tendency to exclude non-cooperative partners from further communication seems to exclude the possibility of an imitation strategy.