Given the importance of economic interactions in European societies, we have relatively little knowledge about children’s decision-making in an economic context. In this work, I tested 802 children aged from 14 months to 10 years in experimental situations based on an exchange task in order (1) to determine the age from which children understand that they can use gifts and exchanges as means to maximize their gain, (2) to test whether they understand the temporal cost associated with an exchange, (3) to study whether they are able to adjust their investment according to the exchange partner(s), and (4) to evaluate their capacity to take a risk during an exchange. For each question, I aimed at identifying potential parallels between the efficiency of economic decisions and the stages of cognitive development already known in children. Results revealed a major shift between 18 and 22 months in the ability to give and exchange. Children were able to adjust their waiting time to the quantity of reward being offered from the age of 3. Finally, I found that children aged over 5 could adapt their investment according to the behavior of partners and the risk of losing related to an exchange. It appears that children’s competencies match what is known of the stages of development in numeric competency, temporal judgment and understanding of others’ mental states. This work should be conducted in other societies with different cultural and economic norms in order to assess the generality of the results found in this thesis.
