Preschool children involve a third party in a dyadic sharing situation based on fairness.

To investigate whether preschool children would involve third parties in dyadic sharing situations, we created unequal sharing situations in which one agent had no resources and a child participant and a third-party individual had unequal resources. We analyzed children's tendency to share with the indigent agent and to involve the wealthy agent, whereas the indigent agent elicited sharing from them by means of progressive levels of request. The results showed that 5-year-olds involved the third party to a greater extent than 3.5-year-olds when they had fewer resources than the third party (Experiment 1). Yet, when 5-year-olds had the largest amount of resources, they were less likely to involve a third party but more likely to share themselves (Experiment 2). This study provides the first evidence that the tendency to involve third-party individuals in resource allocation situations develops at the preschool age and that it is based on fairness considerations.