Children across diverse societies exchange reasons to resolve disagreements.

The exchange of reasons in rational discourse is crucial for resolving disagreements. In a preregistered cross-cultural study, 360 5- to 9-year-old children from China, Kenya, and the U.S. (51.6% female) participated in a dyadic decision-making task (data collection: June 2022 to April 2023). Across cultural contexts, children consistently exchanged reasons. Reason-giving was spontaneous-it appeared without prior training-and selective: children provided reasons more often in contexts of disagreement compared to agreement. Chinese children gave reasons at an earlier age than U.S. and Kenyan children. Overall, our findings challenge claims that the exchange of reasons is a Western-unique mechanism for collective decision-making and suggest that, from a young age, children across diverse societies possess key capacities for engaging in rational public discourse.