Based on evolutionary theories, this study analyzes reasons for sharing and retention and the association of these reasons according to age and the presence of conduct disorder symptoms in children. Therefore, the children participated in a prosocial activity, in which they had to decide if they would like to share a prize with his/her classroom best friend. Finally, the experimenter asked them to explain the reasons for his/her decision. The results showed that children considered factors such

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... as reciprocity probability, sharing cost, benefit to the recipient, moral justification and kinship. Furthermore, the conduct disorder symptoms group showed a weak association to social issues and younger children assign greater cost on sharing the prize, compared to older ones. It is possible to understand the reasons provided by the children in the light of evolutionary theories on cooperation, altruism and generosity.