モニター仮説というのがあるらしい(英語コメント)

I mostly believe the input hypothesis is true. Today, I got to know another hypothesis advocated by Krashen, which is the monitor hypothesis. Looking at it, I speculate that in many cases language learners might pursue accuracy in their target language because of this monitoring function achieved through learning, whether it consists of grammar or syntactic knowledge or experiences in that language. In some cases, they might be so attached to the accuracy pursuit that some kinds of emotional obstacles emerge and prevent them from practicing the language because they hate making any mistakes.