Research on social dilemmas in the production of collective goods typically focuses on cooperation problems situated within a particular social group. Factors influencing whether the dilemma is successfully solved are sought at the level of that group or of the individuals belonging to it. There is an ongoing discussion about the applicability of knowledge gained from laboratory experiments to real-life groups (e.g. Guala, 2012 and responses). For example, the limits of punishment (in the presence of retaliation, e.g. Nikiforakis, 2008; Nikiforakis & Engelmann, 2011) and reward (in the presence of reward exchange, e.g. Flache, Bakker, Mäs, & Dijkstra, 2017; Flache & Macy, 1996) as enforcers of cooperation are being explored. Additionally, there are attempts to apply the knowledge gained from laboratory experiments to increasingly practical situations (e.g. Englmaier & Gebhardt, 2016; Fehr & Leibbrandt, 2011; Kraft-Todd, Yoeli, Bhanot, & Rand, 2015).

We believe that there is an additional aspect to the generalizability of research on social dilemmas, which thus far has received little attention. This aspect is the broader social environment within which a group is embedded, specifically the possibility of overlap in group membership. In the present study, we first illustrate the relevance of the broader social structure, and overlap in group membership in particular, by giving an overview of literature outside of the field of social dilemmas which has demonstrated its importance. Then, we focus on some relevant aspects of the social dilemma literature which can serve as starting points for an investigation into the impact of the broader social structure. Finally, we take the first steps of this investigation by experimentally scrutinizing how findings from social dilemma research on monitoring of free-riders apply to multiple-group situations with overlap in group membership.

The present study makes several contributions to the literature. First, to our knowledge, this is the first experimental investigation of behavior in multiple simultaneous public good games with overlap in group membership. Second, we introduce and validate a punishment system suitable for such an experiment. Third, we investigate how imperfect monitoring of free-riders caused by multiple group membership impacts sanctioning and contribution behavior.

Our results illustrate that findings from social dilemma research which are based on single, isolated groups do not necessarily generalize to multiple groups which have some members in common. We find that the broader social context in which a group is embedded is relevant to the solution of social dilemmas within that group.