Cooperation and punishment: The effect of religiosity and religious festival

•We examine how a religious festival and religiosity affect cooperation.•Less religious subjects increased cooperation significantly outside the festival.•Results show a substitution effect between religious and non-religious activities.•Conditional cooperation is an important motivation for subjects.

This paper examines how a religious festival (Ramadan) and the degree of religiosity affect cooperation and costly punishment in a public goods experiment. We find significantly higher cooperation levels outside the festival among less religious people. This behavior is consistent with a substitution effect between religious and non-religious activities.