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...

We develop a model of R&D collaboration in which individual firms carry out in-house research on core activities and undertake bilateral joint projects on non-core activities with other firms. We develop conditions on the profit functions of the firm under which R&D investments in different...

A fundamental question in social sciences is how trust emerges. We provide an answer which relies on the formation of social and economic relationships. We argue that behind trust lies the fact that individuals invest in connections taking into account the potential externalities networks...

This paper experimentally explores how the enforcement of cooperative behavior in a social dilemma is facilitated through institutional as well as emotional mechanisms. Recent studies emphasize the importance of negatively valued emotions, such as anger, which motivate individuals to punish free...

This paper studies behavior in experiments with a linear voluntary contributions mechanism for public goods conducted in Japan, the Netherlands, Spain and the USA. The same experimental design was used in the four countries. Our 'contribution function' design allows us to obtain a view of...

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 influence on...

We report on an experiment designed to explore whether a written expression of disapproval affects future levels of cooperation. In between two identical public goods games, participants play a mini dictator game that, depending on the treatment, either gives or does not give the recipient the...