Economic behavior often takes place in groups of small numbers of people interacting with each other (like work teams, neighborhoods, social networks, etc.). Characteristic of such interaction is the development of (affective) interpersonal relationships, or social ties. According to...

Field evidence suggests that agents belonging to the same group tend to behave similarly, i.e., behavior exhibits social interaction effects. Testing for such effects raises severe identification problems. We conduct an experiment that avoids these problems. The main design feature is that each...