Organizational Psychology

The article presents the results of theoretical and methodological analysis of one of the most important but simultaneously the least explored concepts of social and organizational psychology — the concept of the middle group. A new approach to the interpretation of this concept and its role in the conceptual system of organizational psychology have been presented. There were suggested decisions of some key problems of psychology of groups: the phenomenology of the middle groups, their structural organization, criteria for their differentiation from the small and large groups, group dynamics. There was substantiated that the concept of the middle group can and should be regarded as the leading concept for synthesis of social and organizational psychology. The specific role of this concept in the organizational psychology theory were discussed in the article. The theses about the fundamental heterogenea of medium-sized groups and their hierarchical organization were formulated and developed.