“…In contrast to homogeneous groups, the experimental evidence regarding contributions to public goods in heterogeneous groups is much less conclusive, 5 and evidence on the enforcement of contribution norms in heterogeneous groups is basically absent. 6 3 The success of informal sanctioning in supporting cooperative behavior has been shown to depend on the costs and effectiveness of the sanctioning (Anderson and Putterman, 2006;Carpenter, 2006;Egas and Riedl, 2008;Masclet and Villeval, 2008;Nikiforakis and Normann, 2008;Sutter et al, 2008), the possibility of taking revenge (Denant-Boemont et al, 2007;Nikiforakis, 2008), availability of information (Carpenter, 2007), communication opportunities (Bochet et al, 2006), and cultural factors (Gächter et al, 2008).…”