I don’t speak a lick of Korean. If I listen to the Korean radio station all day long, I won’t acquire any new words unless I understand at least a little bit. On the other hand, if I understand every single word, it will reinforce the neural pathways I have already formed for those words sounds, words, and phrases.
Understanding language is a clear prerequisite to acquisition.
The same is true in a language classroom. If the learner understands too little, she doesn’t acquire much. If the learner understands every single word, she is primed for when a new word pops up unexpectedly. If she understands most words in a particular exchange, she will pick up lots of language.
The sweet spot, therefore, is somewhere in between the two extremes. It is understanding most words in a given interaction.
