Understanding the proximate and ultimate sources of human cooperation is a fundamental issue in all behavioural sciences. In this article we review the experimental evidence on how people solve cooperation problems. Existing studies show without doubt that direct and indirect reciprocity are...

We study public goods game where the contribution efforts are observable. When the players are observed, they contribute more and free-riding diminishes significantly. On the other hand, presence of an audience does not affect the performance of players if there is no strategic aspect of the...