27. 8. 2012. - Seminar: Jelena Grujić and Luis A. Martinez Vaquero


Monday 27 August 2012 3:15PM and 4:15PM
IPB Library

Iterated prisoner's dilemmas experiment: three is a crowd
Jelena Grujic (Universidad Carlos III de Madrid)

Reciprocity or conditional cooperation is one of the most prominent mechanisms proposed to explain the emergence of cooperation in social dilemmas. Recent experimental findings on networked games suggest that conditional cooperation may also depend on the previous action of the player. We here report on experiments on iterated, multi-player Prisoner's dilemma, on groups of 2 to 5 people. We confirm the dependence on the previous step and that memory effects for earlier periods are not significant. We show that the behavior of subjects in pairwise dilemmas is qualitatively different from the cases with more players; After an initial decay, cooperation increases significantly reaching values above 80%. The strategy of the players is rather universal as far as their willingness to reciprocate cooperation is concerned, whereas there is much diversity in their initial propensity to cooperate. Our results indicate  that, for cooperation to emerge and thrive, three is a crowd.

Does intolerance emerge naturally in a reputation world?
Luis A. Martinez Vaquero (Universidad Carlos III de Madrid)

Human beings are the social animals par excellence. In a world where actions are public, reputation becomes a key
element in decision making process. Our own actions will be conditioned by what we think of the others. In a reputation world, we see how certain moral assessments and action rules prevail over others. In order to study this problem, we developed an indirect reputation model in game theory framework. In this model individuals act and judge taking into account both the reputation of the donor and the recipient. We analyzed what morals and actions are stable under the assumption of this model as well as the scenarios where outbreaks of intolerance or tolerance can invade a population.