This paper presents a formal theory of reciprocity. Reciprocity means that people reward kind actions and punish unkind ones. The theory takes into account that people evaluate the kindness of an action not only by its consequences but also by the intention underlying this action. The theory...

In this paper we show that a simple model of fairness preferences explains major experimental regularities of common pool resource (CPR) experiments. The evidence indicates that in standard CPR games without communication and without sanctioning possibilities inefficient excess appropriation is...

We test experimentally an explanation of over and under confidence as motivated by (perhaps unconscious) strategic concerns, and find compelling evidence supporting this hypothesis in the behavior of participants who send and respond to others ́statements of confidence about how well they have...

This paper investigates how heterogeneity in contestants ́investment costs affects the competition intensity in a dynamic elimination contest. Theory predicts that the absolute level of investment costs has no effect on the competition intensity in homogeneous interactions. Relative cost...

We study the stability of voluntary cooperation in response to varying rates at which a group grows. Using a laboratory public-good game with voluntary contributions and economies of scale, we construct a situation in which expanding a group's size yields potential efficiency gains, but only if...

Understanding the roots of human cooperation among strangers is of great importance for solving pressing social dilemmas and maintening public goods in human societies. We study the development of cooperation in 929 young children, aged 3 to 6. In a unified experimental framework, we examine...