An analysis of older and contemporary literature shows that most of our knowledge about the psychical development of man has been gained through observation of changes in the development of individual components of outer manifestations of his psychic activities (developing changes in individual components of his behaviour) without any causal relationship to those outer or inner factors by which these changes are determined. The aim of development psychology, however, is to gain not only as comprehensive and objective a description as possible of the phenomena that are being studied, but also to discover their very substance, their causes, to explain the laws governing the development of these phenomens. Only with this aim in view can the study of these phenomena arrive at conclusions on the basis of which it will be possible to start with a rational guidance of the psychic development of man. If we assess the present state of methods of research into development psychology, whose aim is the study of factors and laws governing the developing changes in the psychic activities of man, we can say that some partial successes have been achieved especially in the study of developing changes in the relatively simple components of these activities. However, if the development psychology is to explain the factors and laws governing the development of the complicated system of man’s psychic activities in the conditions of constantly changing natural and especially social environment, it cannot be satisfied only with the knowledge gained by the study of developing changes in the individual components of these activities; for man’s psychic activities are characterised by qualitatively completely new features and laws of development which cannot be derived from a simple synthesis of bits of knowledge about the factors and laws governing the developing changes in the individual components of this system. The author assumes that a „cybernetic approach“ to the research into the factors and laws governing the developing changes in the psychic activities of man, which are being realised on the basis of a complex and active interaction between the individual and his constantly changing natural and social environment, is one of the possible ways of arriving at a scientifically exact study of the phenomena which, because of their extraordinary complexity, have been so far subject almost exclusively to empiric investigation in development psychology. But he is fully aware of the fact that a phenological analysis of the phenomena investigated is only one of the essential pre-requisites for a further study of developing changes in those mechanisms and processes on the basis of which man’s psychic activities are being realised. Considering the wide range of key methodological problems of contemporary development psychology the author focuses his attention especially on some questions concerning the structure and the ways of behaviour of the systems formed on the basis of mutual functional relationships between man and individual components of his environment and on the problems involved in the study of the influence of individual experience on the psychic activities of man (the author believes that individual experience formed in the process of learning is the basic component of the conditions accounting for the .changes and development of man’s psychic activities.