We study the development of cooperation in 929 young children, aged 3 to 6. In a unified experimental framework, we examine pre-registered hypotheses about which of three fundamental pillars of human cooperation – direct and indirect reciprocity, and third-party punishment – emerges earliest...

Understanding the roots of human cooperation among strangers is of great importance for solving pressing social dilemmas and maintening public goods in human societies. We study the development of cooperation in 929 young children, aged 3 to 6. In a unified experimental framework, we examine...

The formation of economic preferences in childhood and adolescence has long-term consequences for life-time outcomes. We study in an experiment with 525 teenagers how both birth order and siblings’ sex composition affect risk, time and social preferences. We find that second born children are...