Coethnicity: Diversity and the dilemmas of collective action, by James Habyarimana, Macartan Humphreys, Daniel N. Posner, and Jeremy M. Weinstein
通过乌干达坎帕拉300名贫民窟居民的大型田野实验，测试了多种关于种族合作的竞争性解释，发现匿名时同族者并不更合作，但可见时合作显著增加，原因是社会制裁的可能性，而非共同偏好。
The negative consequences of ethnic diversity on African development have been a very popular topic for social scientists in recent years, with a flood of articles linking diversity and low economic growth, conflict, inequality, and poor public goods provision. Yet none of this scholarship attempted to investigate the mechanism by which diversity harms development – or not, at least, until the four authors reviewed here launched a project in Uganda to answer this question. A decade later, this book is the result. An expanded version of an article published in the American Political Science Review in 2007 by the same authors, Coethnicity uses a large field experiment of a random sample of 300 slum dwellers in Kampala to test a variety of competing explanations for ethnic cooperation. The residents were asked to play a number of different games with each other, including the famed prisoner’s dilemma game, the puzzle game (where subjects had to work together to complete a puzzle) and the dictator game (where subjects are given a sum of money, which they can distribute to other players), among others. The results indicated that coethnics are not more likely to cooperate and be altruistic to each other when the games are played anonymously, but that this result changes when players can see each other, which induces much more coethnic cooperation. To explain this result the authors suggest that it is the possibility of social sanctions that enforces cooperation, especially since the ‘egoists’ who would not otherwise cooperate with coethnics only did so when they became worried that they could face punishment for their activities. Coupled with additional evidence that members of the same ethnic groups do not seem to share the same preferences, the findings thus support the idea that ethnic cooperation happens because of the way ethnicity eases the monitoring and identification of transgressers. Thus, the authors argue, efforts to enhance cooperation in developing countries should focus less on promoting ethnic homogeneity and more on improving citizens’ information about public policies and their ability to hold politicians to account.