SUMMARY
Goal. To describe and present the new scientific theory developed by the co-authors - a system of generalized facts, knowledge and experience regarding the disclosure of the versatility of the genesis of psycholinguistic phenomena characteristic of preschool children. Methods. A complex of theoretical methods of analysis, research synthesis and generalization of a large number of sources was used: firstly, theoretical and conceptual approaches to children’s language and speech and its purposeful formation and development; secondly, empirical data obtained by various scientists working in this issue, as well as data of the own empirical research.Results. The main postulates of the theory of L1 acquisition and speech development presented as an integration of modern interdisciplinary knowledge and practice of the research and project activities, synthesized with a scientific purpose in a set of 14 modules: (1) vector of speech operations and speech actions development; (2) the place and role of systematic learning in L1 acquisition and speech development; (3) the role of implicit language and other types of knowledge in the formation of speech operations; (4) the role of metalanguage and metaspeech knowledge, reflection on speech and objectification of language in the formation of speech acts; (5) levels of awareness in the formation of speech acts; (6) the relationship between speech operations and actions and speech and language abilities, that is, language competences and speech competences; (7) interdependence of linguistic, psycholinguistic and psychological units in the development of speech activity; (8) the role and place of psycholinguistic units in the development of speech; (9) the role and place of psychological units in the formation of speech activity; (10) the role and place of language units in the formation of speech activity; (11) relationship between speaking and learning activities; (12) psycholinguistic prerequisites for the formation of speech activity; (13) psycholinguistic and didactic conditions for purposeful formation of speech activity; (14) relationship of speech operations with other types of operations.Conclusions. The presented theory is an internally non-contradictory system of scientific concepts, views and ideas of its developers, which in a generalized form reveal the essential properties and regular connections of such a psycholinguistic reality as the evolution of the individual language of preschoolers and children’s speech, on the basis of which their explanation is achieved. This theory as an integrative set of principles not only reflects the understanding presented in world science, but is also based on empirical research, on a deep insight into the essence of the genesis of speech phenomena, which occurs in the child’s psycholinguistic nature.