For example, oral speech originates when a baby, initially lacking command of language, is involved in dialogue with his mother who is talking with the baby while she is attending his needs. In the course of the interaction with the mother, elements of the dialogue, words and phrases are internalized by the baby, and form the basis of endophasia and verbal thinking.

According to this theory, human psyche development is socio-culturally – historically specific. Development of human psychic functions is mediated by culture tools, which makes it different from the development of other living species. Human development, as Vygotsky stated, "switches from the natural path of development to the cultural one" when the "ignition" of the latter occurs in the course of socialization.

Leontiev developed the ideas of his predecessors in his own way, so that neither Vygotsky nor Rubinstein fully agreed with his reasoning, so that they both had perpetual discussions with Leontiev and even incurred personal enmity. So Leontiev's theory is justly considered to be an original one, not a mere derivative from the two above mentioned.

What were the main points of Leontiev's theory? What points has he added to the three propositions of AT that refer to Rubinstein?

1. Psyche is the result of the internalization of processes of outward activity. It is a derivative of the outward process, the outward process internalized.

2. The structure of psychic processes is isomorphic to the structure of outward activity from which psyche is a derivative.

The latter proposition he believed to be the essential one and the key to psychological analysis.

These propositions can be considered rather as elaborations of Rubinstein's proposition B, concerning how psyche is shaped, but these elaborations are more narrow and one-sided interpretations of Rubinstein's general formula. Rubinstein considers the interaction between the individual with the environment as a substrate generating psyche. But this does not mean that material interaction is the only and even the main factor, determining psychic development. His stressing of internal subjective mediation of external stimuli should not be underestimated. The inner, the subjective (and first of all motivational phenomena), for Rubinstein determined not only the objective process of interaction with the environment (external), but also the subjective experiencing of this interaction (internal), thus, psyche formation can never be viewed as a straightforward one-sided process of internalization of the outward processes.

Leontiev's theory might be considered to be a simplified approach: it is very straightforward, too straightforward, perhaps. When foreign colleagues blame RAT for it: "(1) relies on unidirectional instead of a theoretically more plausible dialectical view of culture-individual relationships; (2) focuses in analyses on activities without taking into account the individual involved in the activity at the same time" (Toomela, 2000, p.298), – it is all true as far as Leontiev's theory is concerned. Leontiev consistently refused "to look inside the individual". He is emphasizing, for example, the difference between needs and motives, he limits his analysis to motives, to how they structure activity, and turns away from the problem of the needs (Leontiev, 1978).

He considered that needs are the attributes, the inalienable properties of the individual, denoting something that is really necessary for survival. For example, the need for food can be described in terms of proteins, fats, carbohydrates and vitamins, etc., necessary to ensure homeostasis. Needs can be either conscious or unconscious. A motive Leontiev defined as something which an individual fancies that he needs. For example, a motive relevant to the necessity for food can be a pastry or a beefsteak. To engender activity a need has to be "embodied" in a motive and the latter serves as a goal for the active interaction with the environment: a motive determines whether we cook pastries or beefsteaks. A need not "embodied" in a motive cannot engender activity, and produces only a stirring state of excitation, like hunger in a situation when no food is available.

Not all motives adequately respond to needs: the "embodiment" can be fallacious. Nevertheless, these fallacious motives engender activity in the same way as adequate motives do, and their fallacious nature shows only at the end, when the goal is achieved, but instead of satisfaction and positive emotions an individual suffers havoc and devastation. The idea of fallacious motives, however promising it is, did not become a focus in Leontiev's investigations but was just a support for him to limit his analysis to motives, to how they structure activity.

Leontiev developed a specific mode of analysis of psychic processes and a set of directions for how to perform this analysis:

• Activity should be considered as a system in which structure is determined by the Motive (the Target, the Aim);

• Activity components are Acts, which are determined by situations, in which Targets are presented, i.e. by conscious goals;

• & Acts are composed of Operations, which are determined by means, available in actual situations, including tools, motor skills of the subject and his psycho-physiological functions.

So, scientific analysis performed in compliance with this theory should explain psychological contents of the points described above: targets, situations and means of the behavioral process.

The latter proposition he believed to be the essential one and the key to psychological analysis. Under the supervision of Leontiev much experimental and theoretical research was performed at the Moscow State University. Mostly known is the conception of formation of mental operations developed by Piotr Y. Galperin (1902–1989). The above – mentioned idea of Leontiev, that the structure of psychic processes is isomorphic to the structure of outward activity from which psyche is a derivative, was explained and developed by Galperin. According to his theory, initially an operation (for example counting) is carried out outwardly (counting sticks, for example), and then, passing through a number of certain phases, it is internalized and turns up as a mental operation. Leontiev's ideas have been put to educational practice by Elkonin and Davidov (Davidov, 1986) whose works laid foundations of