The transition from curiosity to cognitive activity helps children to make the first steps to inquisitiveness and develops cognitive activity as means of various play and practical problems' solution. Role of joint activity in development of preschoolers' cognitive activity is far from having single meaning. It depends on qualitative peculiarities of group interaction and is determined by the goals set and results obtained. When cognitive problem is the object of interaction, mutual exchange and mutual enrichment take place. If the object of interaction is the choice of solution, the group does not influence cognitive sphere of its participants.