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Abstract

New behavioural and neuroscientific evidence on the development of fairness behaviours demonstrates that the signatures of human fairness can be traced into childhood. Children make sacrifices for fairness (1) when they have less than others, (2) when others have been unfair and (3) when they have more than others. The latter two responses mark a critical departure from what is observed in other species because they enable fairness to be upheld even when doing so goes against self-interest. This new work can be fruitfully combined with insights from cognitive neuroscience to understand the mechanisms of developmental change.

Fairness is a hallmark of our species's ability to maintain cooperative relationships with large numbers of unrelated — and often unfamiliar — others. However, there is much debate over the psychological foundations of this sense of fairness. Which aspects of fairness are engrained in our biology and which depend on learned social norms? What are the psychological mechanisms and motivations that give rise to human fairness? Why does fairness appear to drive decisions in some contexts but not others? To answer these questions, it is critical to understand how fairness emerges in child development, as studies of adults alone do not allow us to differentiate between psychological processes that are acquired through socialization and those that have deeper biological roots. Indeed, a complete understanding of any behaviour requires a description of its developmental course and an examination of what causes behavioural change over the lifespan1,​2,​3.

Studies of child development can provide unique insight into the psychology of fairness in important ways: first, developmental data can help to identify the aspects of fairness that are foundational and those that are more malleable. Second, charting how fairness behaviour changes across development can shed light on the specific cognitive mechanisms that enable its emergence and expression. Finally, combining insights from development with work examining how fairness is instantiated at the neural level can help us to understand the psychological foundations on which the human sense of fairness is built.

In this Review, we appraise and integrate recent developmental and neuroscientific evidence on fairness. The resulting neurodevelopmental perspective provides novel insights into the foundations of fairness in our species. First, we argue that the signatures of our uniquely human sense of fairness are present in childhood. We then summarize the current state of knowledge for neural mechanisms that support fairness and highlight recent work on the developmental neuroscience of fairness. Last, we identify key neural processes that change during childhood and propose how the developmental integration of these systems can explain the temporal emergence of the human sense of fairness.