AN INTRODUCTION TO THE THEORY OF ACTIVITY To the memory of my dear friend Gregory Bedny

In this paper we present a brief overview of general, applied and systemic-structural activity theories. Activity Theory (AT) was created in the former Soviet Union by three prominent scholars - Vygotsky, Leont'ev and Rubinshtein. General activity theory was first introduced by the Sergey Rubinshtein (1958). It was further developed in the works of Leont'ev (1977) and Vygotsky (1978). The development of AT was shaped by the practical demand of ergonomics, engineering psychology and education. The important requirement of psychological studies in the former Soviet Union was a possibility to utilize psychology for practical application and particularly in the study of human work and learning. Thus, the effect of practical application on AT is not accidental. With the development of mechanization and automation in the industry, in transport, in the military sphere and in other modern fields of human activity it became obvious, that the direct application of the general activity theory for the study of human activity was not possible. The theory received recognition in the West, and particularly in the USA. We will consider basic concepts of activity theory and will outline some difficulties which Western scientists experience in their interpretation and application of the theory in science and practice. To the response of technological progress, a more advanced theory, namely, applied activity theory (AAT), was created in the works of a number of Soviet psychologists in the 1970s. The Rubinstein-Leont'iev-Vygotsky's general activity theory became the theoretical and philosophical basis of applied activity theory. Creation of AAT was the first step in an attempt to apply activity theory to the study of human activity. The further development of applied activity theory led to the creation of the systemic-structural activity theory (SSAT) as an independent direction of AAT. The theory was founded by Gregory Bedny1 (2007). The creation of SSAT has greatly advanced the science of activity because it can be applied to the study and practice of human work. The focus of this article will be mostly on the Systemic-Structural Activity Theory (SSAT).