“…In this respect, it is interesting to note that many researchers implicitly assume such an equalcontributions norm when they analyze punishment behavior in public good games. For example, it is commonly assumed that punishment is motivated by deviations from either the average contribution Gächter, 2000, 2002;Anderson and Putterman, 2006;Sefton et al, 2007), the punisher's contribution (Gächter et al, 2008;Egas and Riedl, 2008;Sutter et al, 2008), or both (Masclet et al, 2003;Masclet and Villeval, 2008;Nikiforakis, 2008). In all these cases an equal-contributions norm is assumed.…”