This paper examines the impact of costly punishment on cooperation in public goods experiments. The authors find that free riders are heavily punished, even when punishment does not provide material benefits to the punisher. The intensity of punishment increases with the deviation from the group standard, leading to a significant increase in cooperation levels. In the presence of costly punishment opportunities, almost complete cooperation can be achieved and maintained, despite the standard assumptions of rationality and selfishness. The study also shows that free riding causes strong negative emotions among cooperators, which supports the hypothesis that emotions are guarantors of credible threats. The results suggest that emotion-based punishment plays a crucial role in maintaining cooperation and social norms in various social interactions.This paper examines the impact of costly punishment on cooperation in public goods experiments. The authors find that free riders are heavily punished, even when punishment does not provide material benefits to the punisher. The intensity of punishment increases with the deviation from the group standard, leading to a significant increase in cooperation levels. In the presence of costly punishment opportunities, almost complete cooperation can be achieved and maintained, despite the standard assumptions of rationality and selfishness. The study also shows that free riding causes strong negative emotions among cooperators, which supports the hypothesis that emotions are guarantors of credible threats. The results suggest that emotion-based punishment plays a crucial role in maintaining cooperation and social norms in various social interactions.