External validity is the problem of generalizing results from laboratory to non-laboratory conditions. In this paper we review various ways in which the problem can be tackled, depending on the kind of experiment one is doing. Using a concrete example, we highlight in particular the distinction...

Nudge policies are typically justified from paternalistic premises: nudges are acceptable if they benefit the individuals who are nudged. A tacit assumption behind this strategy is that the biases of decision that choice architects attempt to eliminate generate costs that are paid mainly by the...

Group membership increases cooperation in social dilemma games, altruistic donation in dictator games, and fair offers in ultimatum games. While the empirical study of group action has grown rapidly over the years, there is little agreement at the theoretical level on exactly why and how group...

Recent experiments with the Dictator Game (and the ensuing discussions) have been affected by considerable confusion regarding the purpose of this design. A common complaint is that the design gives rise to fragile regularities and therefore is of little use for theory-testing. We take issue...

According to a tradition that goes back to David Hume, social conventions have a natural tendency to turn into norms. Normativity increases compliance and stabilizes individual behaviour in spite of changes in incentives. In this paper we report experimental data that confirm this insight and...

Group membership is a powerful determinant of social behaviour in a variety of experimental games. Its effect may be channelled primarily via the beliefs of group members, or directly change their social preferences. We report an experiment with a prisoner's dilemma with multiple actions, in...

Group membership increases cooperation in social dilemma games, altruistic donation in dictator games, and fair offers in ultimatum games. While the empirical study of group action has grown rapidly over the years, there is little agreement at the theoretical level on exactly why and how group...