Abstract Impersonal prosociality—the inclination to trust and cooperate outside one’s social circle—varies widely across societies. This study examines whether formalizing land property rights in a society previously governed by informal use rights expands the circle of prosocial behaviours. We hypothesized that formal land property institutions, backed by state enforcement, reduce reliance on local social networks for property protection, potentially broadening social interaction and fostering prosociality toward strangers. To test this hypothesis, we leverage a large-scale land rights formalization programme in Benin, implemented as a randomized control trial. Using lab-in-the-field experiments, vignette studies and attitudinal surveys, we find no evidence that the reform increased the circle of trust, trustworthiness or prosocial norm enforcement toward strangers in other villages. Instead, exploratory analyses suggest that formalized land rights tend to enhance prosociality among co-villagers. While we examine changes in kinship structures as a possible mechanism, results remain inconclusive. These findings suggest that land tenure reforms may reshape social behaviour by reinforcing local ties rather than by broadening prosociality beyond immediate communities. This article is part of the theme issue ‘Transforming cultural evolution research and its application to global futures’.
Fabbri et al. (Mon,) studied this question.