Perhaps Vygotsky’s most important contribution concerns the inter-relationship of language development and thought. This concept, explored in Vygotsky’s book Thought and Language, establishes the explicit and profound connection between speech (both silent inner speech and oral language), and the development of mental concepts and cognitive awareness. It should be noted that Vygotsky described inner speech as being qualitatively different from normal (external) speech. Although Vygotsky believed inner speech developed from external speech via a gradual process of internalization, with younger children only really able to “think out loud,” he claimed that in its mature form inner speech would be unintelligible to anyone except the thinker, and would not resemble spoken language as we know it. Hence, thought itself develops socially.
“Zone of proximal development” (ZPD) is Vygotsky’s term for the range of tasks that are too difficult for the child to master alone but that can be learned with guidance and assistance of adults or more-skilled children. The lower limit of ZPD is the level of skill reached by the child working independently. The upper limit is the level of additional responsibility the child can accept with the assistance of an able instructor. The ZPD captures the child’s cognitive skills that are in the process of maturing and can be accomplished only with the assistance of a more-skilled person. Scaffolding is a concept closely related to the idea of ZPD. Scaffolding is changing the level of support. Over the course of a teaching session, a more-skilled person adjusts the amount of guidance to fit the child’s current performance. Dialogue is an important tool of this process in the zone of proximal development. In a dialogue unsystematic, disorganized, and spontaneous concepts of a child are met with the more systematic, logical and rational concepts of the skilled helper.