Learning efficiency of individual members of a training group has been studied as a function of the group size under real-life learning conditions. It is shown that in collective-type groups efficiency of learning increases up to a certain limit of the group size. It has been assumed that this fact must be explained by the activating influence of the group on its particular members. Further theoretical analysis of the assumption makes it possible to suggest a hypothesis that this activating effect is a result of the .specifically collective activity which provides conditions for generation and exchange of motives between the partners in common acts.