Language Acquisition Hypotheses 

Much of the research into Second Language Acquisition comes from the work of Stephen Krashen. Krashen's research has proposed the Monitor Model with five hypotheses regarding the processes around language development. The five hypotheses described below contribute to working body of research regarding language developement through conscious and unconscious processes. Key features of the hypotheses that are still widely accepted are described below. 

Source: Cirrus Praxis English to Speakers of Other Languages 5352 Study Guide 2018-2019 (Pg 39-41)