Interaction hypothesis

The Interaction hypothesis is a theory of second-language acquisition which states that the development of language proficiency is promoted by face-to-face interaction and communication. The idea existed in the 1980s, but is usually credited to Michael Long for his 1996 paper The role of the linguistic environment in second language acquisition. There are two forms of the Interaction Hypothesis: the "strong" form and the "weak" form. The "strong" form is the position that the interaction itself contributes to language development. The "weak" form is the position that interaction is simply the way that learners find learning opportunities, whether or not they make productive use of them.

Similarly to Krashen's input hypothesis, the interaction hypothesis claims that comprehensible input is important for language learning. In addition, it claims that the effectiveness of comprehensible input is greatly increased when learners have to negotiate for meaning. This occurs when there is a breakdown in communication which interlocutors attempt to overcome. One of the participants in a conversation will say something that the other does not understand; the participants will then use various communicative strategies to help the interaction progress. The strategies used when negotiating meaning may include slowing down speech, speaking more deliberately, requests for clarification or repair of speech, or paraphrases.

Interactions often result in learners receiving negative evidence. That is, if learners say something that their interlocutors do not understand, after negotiation the interlocutors may model the correct language form. In doing this, learners can receive feedback on their production and on grammar that they have not yet mastered. The process of interaction may also result in learners receiving more input from their interlocutors than they would otherwise. Furthermore, if learners stop to clarify things that they do not understand, they may have more time to process the input they receive. This can lead to better understanding and possibly the acquisition of new language forms. Finally, interactions may serve as a way of focusing learners' attention on a difference between their knowledge of the target language and the reality of what they are hearing; it may also focus their attention on a part of the target language of which they are not yet aware.

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