Russian AT is an essentially materialistic theoretical approach. Materialistic psychological perspectives, such as behaviorism and psychobiology are mostly based on a straight-forward interpretation of Darwin's theory, putting the sources and the causes of the development in the external world. It is the stimulus, the change of the environment, which is the cause of the change of the behavior and the structure of living beings for these theories. Dialectical materialism, realized in the Russian AT, on the contrary, accounts for both continuity and discontinuity, seeking internal origins and causes of development, which are viewed as a result of resolving internal conflicts. This entailed a primary focus on ruptures and discontinuities in evolution: on the principle differences between animate and inanimate matter and between human and animal. The former was implemented in wide-scale investigations of sensory processes, supposed to be adjacent to the border between physiological and psychological aspects of reality, and the latter accounts for enhanced development and specific character of Soviet comparative psychology (Mironenko, 2009b; 2010).

There is an important point of linguistic origin which has caused confusion in the notions "Sub'ekt Approach" and "Theory of Dejatelnost" in the international literature, which we have to consider. There are two key words in the context of the AT:

• Sub'ektnost (субъектность),

• Dejatelnost (деятельность).

The translation of both usually turns out to be the same: Activity. But in Russian these words differ in their meaning. And moreover – there is another Russian word – "activnost", which is precisely translated as "activity". So the English translation does not allow us to obtain the right understanding of the difference.

Let's consider the exact meanings of the concepts "Sub'ektnost" and "Dejatelnost".

The concept of Sub'ekt (and "Sub'ektnost" for a quality to be a Sub'ekt) refers to S. L. Rubinstein whose main idea was that Psyche is a procreation of active interaction of individual with the environment. Sub'ekt means somebody whose activity is generated by his own needs, who is choosing and pursuing his own aims, serving his own purposes: a self-determined and self-actualizing agent[17]. According to Rubinstein, Psyche has developed in the course of evolution as a means for a living being to promote its survival and to pursue its needs. Psychic structure is determined by the inner needs of the individual; so to reveal a psychic set up, the needs should be analyzed. It is the inner sources of activity which Rubinstein focused on.