Cumulative activity as a genetically original unit of mental development

The presented study is aimed at forming the first activity in deafblind children. The course of development of the deafblind, as presented by the author, contradicts the postulates adopted in child psychology, for example, about the leading activity of communication among the baby and the need for speech for the joint and independent activity of the child. The study confirms the hypothesis of cumulative activity as a genetically original unit of mental development, but it is devoid of the sign of speech mediation.