Professor Stephan D. Krashen is one of the most well-known experts of linguistics. His theory of second language acquisition, known as the Monitor Model, consists of five interconnected hypotheses: (1) the acquisition/learning hypothesis, (2) the natural order hypothesis, (3) the monitor hypothesis, (4) the input hypothesis, and (5) the affective filter hypothesis (Freeman & Freeman, 2011, p. 113).
The acquisition/learning hypotheses refers to the idea that people are actually able to develop a second language through two methods: (1) by acquisition and (2) by learning. Acquisition is a subconscious process in which a learner is unaware of what they are gaining. It bases itself on how people communicate among each other through real and meaningful activities. Learning, on the other hand, is the product of formal instruction. It focuses on learning correct grammar and following the rules of target language.
The natural order hypothesis focuses on the idea that whatever the language one is trying to learn, there is a particular order with which that language learning progresses. This hypothesis suggests that this natural order of acquisition occurs independently of deliberate teaching and therefore teachers cannot change the order of a grammatical teaching sequence. According to Freeman & Freeman, “The natural order applies to language that is acquired, not language that is learned”(2011, p117).
The monitor hypothesis bases itself on correcting the language of a language learner. It’s basically an editor that “provides us with rules we can use to monitor our output as we speak or write” (p 118). The monitor is a way of evaluating how well a student can communicate in the second language.
The input hypothesis is based on comprehensible input, when the language acquisition students receive can actually be understood by them. When input is comprehensible, students are able to understand the essence of what is being said or presented to them. “To ensure that the input is comprehensible, teachers can use pictures, gestures, tone of voice, and hands-on activities” (Freeman & Freeman, 2004, p. 38).
The affective filter hypothesis “explains the role of affective factors in the