We report on an experiment using video technology to manipulate pre-play communication protocols in the lab and to study purely social effects of communication on donations and discrimination between potential receivers. The experimental design eliminates strategic factors by allowing two...

To explain why pre-play communication increases cooperation in games, one refers to a) strategic causes such as efficient communication or reputation effects, and b) changes in the utilities due to social processes. Hitherto experimental support for both explanations is mixed and confounded. Our...