Who would you save? Children and mothers' life-or-death decisions

The principle of equal human worth is widely endorsed, yet real-world situations often require trade-offs. This raises a fundamental question: Do individuals truly value all human lives equally from an early age, or do they differentiate based on salient attributes? In a cross-sectional study, children aged 5-10 years (N = 253, 47% female) and their mothers made binary life-or-death choices between two individuals differing in age and sex. Results showed that even the youngest children did not value all lives equally. With age, children increasingly prioritized younger individuals, plausibly reflecting a growing understanding that older people have less time left to live, and showed reduced same sex ingroup preference. Machine learning models predicted older children's choices more accurately, suggesting that decision-making becomes more systematic and predictable with development. Mothers prioritized younger and female lives, with the strongest female preference emerging when the two individuals differed in sex but not age. Framing also influenced judgment: saving vs. leaving behind altered the strength of the preference for younger lives. These patterns align with social norms and gender stereotypes (e.g., protection of "vulnerable" groups, gendered expectations of helpfulness and susceptibility to harm). Evolutionary frameworks, such as reproductive value and parental investment, offer potential explanations for why such norms and stereotypes seem pervasive. Overall, the findings indicate that the valuation of human lives is initially not egalitarian, becomes increasingly structured across childhood, and adult priorities may arise from the interplay between evolved caregiving heuristics and fairness norms.