The document discusses how learners acquire a new language. It mentions that a learner's motives, needs, attitudes, and emotional states filter what they hear from the language, affecting the quality of their acquisition. This filtering determines what language models and parts of the language the learner focuses on first, as well as how quickly and for how long they acquire the language. The filtering also guides the overall acquisition process by limiting what can be learned and rejecting material that does not fit the learner's emerging language system.