From David Long
All of the evidence we have gathered during the past several decades shows that those students who remain silent, refusing the temptation to ‘try to speak’, excel, whereas those students who ‘try to speak’ set limits on their ability to both learn and to use the language. We have never seen a single exception to this rule! The fact is, practicing to speak actually slows down the learning process! Much of the problem here is that we always want to gauge our progress by equating it with speaking ability. Speaking is one of the last parts that emerge in language acquisition. At our school, we recommend a silent period between 600 to 800 hours of instruction.
Automatic Language Growth