We investigate leading by example in a public goods game in scenarios with and without intergroup competition. Leading by example is implemented via a sequential decision protocol. We examine both one-shot and repeated interaction and make use of the strategy method to characterize followers'...

Koukoumelis et al. (2010, 2012) have shown that one-way communication enhances contributions to public goods. We investigate the effectiveness of one-way communication, when the benefits from the public good are asymmetric and the sender of a message is the main beneficiary of cooperation. Our...

Envy is often the cause of mutually harmful outcomes. We experimentally study the impact of envy in a bargaining setting in which there is no conflict in material interests: a proposer, holding the role of residual claimant, chooses the size of the pie to be shared with a responder, whose share...

Numerous studies suggest that communication may be a universal means to mitigate collective action problems. In this study, we challenge this view and show that the communication structure crucially determines whether communication mitigates or intensifies the problem of collective action. We...

We experimentally test the social motives behind individual participation in intergroup conflict by manipulating the framing and symmetry of conflict. We find that behavior in conflict depends on whether one is harmed by actions perpetrated by the out-group, but not on one's own influ- ence on...

We enrich the choice task of responders in ultimatum games by allow- ing them to independently decide whether to collect what is offered to them and whether to destroy what the proposer demanded. Such a multidimensional response format intends to cast further light on the motives guiding...

Although one may hope to achieve equality of stated profits without enforcing it, one may not trust in such voluntary equality seeking and rather try to impose rules (of bidding) guaranteeing it. Our axiomatic approach is based on envy-free net trades according to bids which, together with the...

Unlike previous attempts to implement cooperation in a prisoners' dilemma game with an infinite horizon in the laboratory, we focus on extended prisoners' dilemma games in which a second (pure strategy) equilibrium allows for voluntary cooperation in all but the last round. Our four main...

People exhibit group reciprocity when they retaliate, not against the person who harmed them, but against somebody else in that person's group. Group reciprocity may be a key motivation behind intergroup conflict. We investigated group reciprocity in a laboratory experiment. After a group...

In experiments, people behave more cooperatively when they are aware of an external threat, while in the field, we observe surprisingly high levels of cooperation and altruism within groups in conflict situations such as civil wars. We provide an explanation for these phenomena. We introduce a...