An experiment has been performed with the view to establish how different moral categories possessed by adolescents can be used as means of stimulation in them of learning motivation. The categories are shown to be developed to different degrees in different kinds of learning activity, and special efforts on the part of an adolescent are needed to make them operative. In particular it requires mastering of both the learning operations as such and the system of communication with others where the value of those operations becomes evident. Moral categories appear to be a means of realization by an adolescent of his personal responsibility for maintaining obligatory requirements to learning.