According to the interaction hypothesis (Long, Gass), second language acquisition occurs when learners interact in conversation with native speakers and/or each other.
Interactionist models can be represented thus:
Aspects of the input are noticed (apperception), comprehended and become intake to be integrated into interlanguage and available for production (output).
Interaction is thought to improve intake and integration by creating the need to negotiate meaning at points of communicative breakdown, and through various types of feedback (recasts, reformulations) which may be integrated into learner production (uptake).
This hypothesis suggests that feedback obtained during conversational interaction promotes interlanguage (IL) development because it:
Connects input, internal learner capacities, particularly selective attention, and output in productive ways.
In this view, classroom interaction is important not just to provide practice opportunities, but because interaction actually triggers acquisitional processes:
Conversational interaction in a second language forms the basis for the development of language rather than being only a forum for practice of specific language features.