In the theoretical analysis of the general structure of activity as presented in the fundamental work of L. S. Vygotsky and A. N. Leont'ev, cooperation among the participants in a joint activity is viewed as the source of new mental functions. Under conditions of cooperation, an activity that is initially shared by those participating in it emerges as an original and fundamental foundation for the development of forms of individual activity. Thus, L. S. Vygotsky wrote, "Any function in the cultural development of the child appears twice, on two levels: first as a social function, and then as a psychological function, first as something taking place between people, a category based on relationship between minds, an intermental category; later, this psychological function occurs within the child, as an intramental category" [2. Pp. 197-98].