Recent research at the cross between cognitive and social sci- ences is investigating the cognitive mechanisms behind coop- erative decisions. One debated question is whether cooperative decisions are made faster than non-cooperative ones. Yet em- pirical evidence is still mixed. In this paper we explore the implications of individual heterogeneity in social value orien- tation for the effect of response time on cooperation. We con- duct a meta-analysis of available experimental studies (n=8; treatments=16; 5,232 subjects). We report two main results: (i) the relation between response time and cooperation is mod- erated by social value orientation, such that it is positive for individualist subjects and negative for prosocial subjects; (ii) the relation between response time and cooperation is partly mediated by extremity of choice. These results suggest that highly prosocial subjects are fast to cooperate, highly individ- ualist subjects are fast to defect, and subjects with weaker pref- erences make slower and less extreme decisions. We explain these results in terms of decision-conflict theory.

We survey the growing literature on group formation in the context of three types of social dilemma games: public goods games, common pool resources, and the prisoner's dilemma. The 62 surveyed papers study the effect of different sorting mechanisms-endogenous, endogenous with the option to play the game, and exogenous-on cooperation rates. Our survey shows that cooperators are highly sensitive to the presence of free-riders, independently of the sorting mechanism. We complement the survey with a meta-analysis showing no difference in terms of cooperation between studies implementing an endogenous and exogenous sorting. What is more, we find that it is no more likely for a cooperator to be matched with like-minded partners in endogenously formed groups than in exogenously formed groups. These observations are related. As we show in the survey, the success of a sorting method in matching like-minded individuals and the levels of cooperation are closely interlinked. * For valuable insights at various stages of this work, we wish to thank Rachel Croson, Fabrice Le Lec, Marie-Claire Villeval and the participants at the IMEBESS meeting in Barcelona, the ASFEE meeting in Rennes, and at the Cooperation: Interdisciplinary Methods Workshop in Lille. We are also grateful to the authors who responded to our various requests on the ESA forum.

We survey the growing literature on group formation in the context of three types of social dilemma games: public goods games, common pool resources, and the prisoner’s dilemma. The 62 surveyed papers study the effect of different sorting mechanisms – endogenous, endogenous with the option to play the game, and exogenous – on cooperation rates. Our survey shows that cooperators are highly sensitive to the presence of free-riders, independently of the sorting mechanism. We complement the survey with a meta-analysis showing no difference in terms of cooperation between studies implementing an endogenous and exogenous sorting. What is more, we find that it is no more likely for a cooperator to be matched with like-minded partners in endogenously formed groups than in exogenously formed groups. These observations are related. As we show in the survey, the success of a sorting method in matching like-minded individuals and the levels of cooperation are closely interlinked.