The methodological basis of the study was the theory of the activity approach to the development of the psyche in ontogenesis (A.V. Zaporozhets, A.N. Leontiev, D.B. Elkonin, etc.); theoretical provisions on the structure of the defect (L.S. Vygotsky, T.A. Vlasova, V.I. Lubovsky, M.S. Pevsner, etc.); theory of psychological and clinical diagnostic criteria (S.S.Lyapidevsky, E.M. Mastyukova, O.V. Pravdina, A.M. Smirnova, M.E. Khvattsev, etc.); the position on the leading role of education and upbringing in the psychological development of the child (L.S. Vygotsky).