Prosociality declines after a collective ritual: Evidence from a patron saint festival in Oaxaca, Mexico

The cross-cultural ubiquity of costly collective rituals presents a puzzle. Researchers have proposed that collective rituals enhance group solidarity, facilitating these rituals’ spread through intergroup competition. Accordingly, studies indicate that collective rituals can foster cohesion and cooperation in lab and real-world settings. We test this hypothesis in a novel, naturalistic setting: patron saint festivals (fiestas) in indigenous communities of Oaxaca, Mexico. In this preregistered natural experiment, we used mixed methods to study changes in cohesion, prosocial attitudes, and cooperation after a fiesta in one Zapotec village. Our within-subjects design included 36 survey participants, 25 of whom also completed a Public Goods Game. Contrary to prior research, we find evidence of declines in altruism and cooperation, and no change in cohesion. Nonetheless, the fiesta is a huge cooperative endeavor. While the sample is constrained by the community’s size and this naturalistic event does not offer a fully controlled field experiment, these results offer important nuance to our understanding of collective ritual.