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α: calibrated so average coauthorship-adjusted count equals average raw count
This paper presents results from a prisoner’s dilemma game experiment with a third party punisher. Third party punishment was frequently observed, in line with previous studies. Despite the prevalence of punishment, having one third party punisher in a group did not make one’s defection materially unbeneficial because of the weak punishment intensity observed. When a third party player’s action choice was made known to another third party player in a different group, however, third party punishment was sufficiently strong to transform the dilemma’s incentive structure into a coordination game, through which cooperation norms can be effectively enforced.