<P> Social interactionist theory is an explanation of language development emphasizing the role of social interaction between the developing child and linguistically knowledgeable adults . It is based largely on the socio - cultural theories of Soviet psychologist Lev Vygotsky, and made prominent in the Western world by Jerome Bruner . </P> <P> Unlike other approaches, it emphasizes the role of feedback and reinforcement in language acquisition . Specifically, it asserts that much of a child's linguistic growth stems from modeling of and interaction with parents and other adults, who very frequently provide instructive correction . It is thus somewhat similar to behaviorist accounts of language, though it differs substantially in that it posits the existence of a social - cognitive model and other mental structures within children (a sharp contrast to the "black box" approach of classical behaviorism). </P> <P> Another key idea within the theory of social interactionism is that of the zone of proximal development . Briefly, this is a theoretical construct denoting the set of tasks a child is capable of performing with guidance, but not alone . As applied to language, it describes the set of linguistic tasks (proper syntax, suitable vocabulary usage, etc .) a child cannot carry out on their own at a given time, but can learn to carry out if assisted by an able adult . </P> <P> The relational frame theory (RFT) (Hayes, Barnes - Holmes, Roche, 2001), provides a wholly selectionist / learning account of the origin and development of language competence and complexity . Based upon the principles of Skinnerian behaviorism, RFT posits that children acquire language purely through interacting with the environment . RFT theorists introduced the concept of functional contextualism in language learning, which emphasizes the importance of predicting and influencing psychological events, such as thoughts, feelings, and behaviors, by focusing on manipulable variables in their context . RFT distinguishes itself from Skinner's work by identifying and defining a particular type of operant conditioning known as derived relational responding, a learning process that, to date, appears to occur only in humans possessing a capacity for language . Empirical studies supporting the predictions of RFT suggest that children learn language via a system of inherent reinforcements, challenging the view that language acquisition is based upon innate, language - specific cognitive capacities . </P>

What are the four skills of a language from the point of view of its acquisition