This paper is based upon the ideas of the psychological school of L. S. Vygotsky, A. N. Leontiev and A. R. Luria and presents a critical analysis of currently popular and allegedly successful projects of teaching human language to apes. The paper shows that the authors of such studies and their promoters ignore qualitative differences between psychological mechanisms of human and animal communication, as well as their functions in behavioral regulation of both. This is explained, in particular, by the fact that the human-animal comparison originates from some visible and functional similarities of certain aspects of their communicative behavior. Moreover, the observed differences are recognized as quantitative distinctions, but not qualitative ones. In this paper a critical analysis of data submitted by such projects is presented. The outcome is as follows. Though apes, especially in vitro, can use some symbolic means (language symbols) to manipulate the behavior of others, none of the animals, subjected to such experiments have acquired an ability to control themselves in the context of certain social (conventional) requirements. Meanwhile, according to L. S. Vygotsky, the arbitrary regulation of one’s own behavior with the use of symbolic means as «psychological tools» is what determines a human as a being, qualitatively different from an animal. Moreover, this arbitrary regulation has emerged in the course of historical development through human labor (common, socially-induced and tool-mediated) activity.

Hence, the conclusion is that if the most important features of human language (its use on the way of mastering one’s own behavior and regulating one’s own mental processes) is ignored, this leads to inadequate interpretation of the data collected in animal behavior studies, as well as to biological reductionism of human activity explanation.

In the course of treating a serious illness, a person is faced with questions related not only to the medical side of treatment, but also with the realizing the sense of the events. This is equally true for both oncology adults and for children.

The paper researches the disease representation in children who suffer from severe diseases. General psychological aspects of the disease situation and the understanding of patient children and the ability to use these concepts in practical psychological help are considered.

The study hypothesizes, first of all, the semantic structure of representation in this group of children having specific characteristics that distinguish them from healthy children. Secondly, data representation having a therapeutic potential can be used as a psychological tool. Mediating function of the psychological tools mentioned is justified in this paper from the perspective of cultural historical approach and the concept of mental health levels. The experimental study was conducted in the specialized pediatric clinics in Moscow, Russia. Control group include students of one of Moscow schools. The study included organization of the experimental situation, criteria for obtaining data, comparative analysis and evaluation.

The hypothesis is confirmed. The characteristic structure of disease representations in patient children reflecting some vector of the disease course is outlined. This makes the study an important practical value as the results may provide a solution to practical issues of medical psychology in assisting patient children. The research offers further studying the semantic sphere of patient children.