The document discusses several theories of second language acquisition, including: 1. Krashen's Input Hypothesis which distinguishes between subconscious language acquisition and conscious language learning, and emphasizes the importance of comprehensible input. 2. Long's Interaction Hypothesis which builds on Krashen and argues that modified interaction between learners and others provides comprehensive input. 3. Research showing that aspects of language like grammar are more easily acquired during childhood, while factors like accent are most influenced by age of acquisition. Overall, age should not deter second language learning.

1. Second Language Acquisition And Applied Linguistics

2. Two sisters at School

16. The cognitive model of Second Language Acquisition Focus to a considerable extent of the learners IV. A SOCIAL CONSTRUCTIVIST MODEL: LONG’S INTERACTION HYPOTHESIS Two preceding theories Krashen’s Input Hypothesis