Authors inspired by Vygotsky's theory of internalization agree that both the child and the adult contribute to the process of internalization. However, in empirical studies of adult-child interaction, the emphasis is mostly on the role of the adult. Moreover, most studies of internalization suppose that the adult, in these interactions, has a teaching role. Observations were made of 10 adult-child dyads, engaged in a construction task. These observations showed that the children contributed actively to the interaction and to the solution of the problem. Despite the restricted task, the adult-child dyads constructed the interaction in different ways, leading to a variety of definitions of the task, some instructive, but others playful, task-oriented or predominantly affective.