"We examine the characteristics and the relative strength of third party sanctions inna series of experiments. We hypothesize that egalitarian distribution norms and cooperationnnorms apply in our experiments, and that third parties, whose economic payoff is unaffectednby the norm violation, may be willing to enforce these norms although the enforcement isncostly for them. Almost two-thirds of the third parties indeed punish the violation of thendistribution norm and their punishment increases the more the norm is violated. Likewise, upnto roughly 60 percent of the third parties punish the violation of the cooperation norm. Thus,nour results show that the notion of strong reciprocity also extends to the sanctioning behaviornof “unaffected” third parties. In addition, these experiments suggest that third partynpunishment games are powerful tools for studying the characteristics and the content of socialnnorms. Further experiments indicate that second parties, whose economic payoff is reducednby the norm violation, punish the violation much more strongly than do third parties. We alsoncollect questionnaire evidence that is consistent with the view that fairness motives andnnegative emotions are a determinant of third party sanctions."