BE THERE !
So what is the lesson to be learned here? We need to BE THERE to provide that input during this period. That means reading to the child a lot, and talking to him/her even more.
This is easier said than done. Answering the child's endless requests for names and explanations, like "mad cow disease," will turn any adult's mind into mush in short order.
It takes high dedication, intense focus and selflessness beyond belief to do this. Typically only well informed or fanatic parents (usually mothers or grandmothers) will do this. Baby sitters and day care attendants (who have other responsibilities) typically will not bother or may not have the time.
The time will pass, however, whether or not the input is provided, and the window will close slowly. If the input has been there, the impact on the child's language development will be profound! You will become impressed with the child's awareness of his/her environment, and the precision of his/her thought processes.