@Cyracuz,
Yes. I know this is a scientific experiment, but when talking about how the environment adapts to the child, I had to think "well any mother (or child rearing father) could tell you that."
A kid tries a new word, mangles it, caregivers break it down to simpler and simpler pieces, until it's easy enough for the kid to get his mouth around, then you shoot back up as the kid quickly master it.
Same with the red and green colored lines. If you had to put it in words, most people would tell you that you play with a kid, you're teaching, they are learning, then they go off and practice what they learned, by themselves.
What I did find interesting is that the kitchen (I'll bet) is the true heart of the home. Notice of course that's where they identified where the word 'water' was said the most. However, the word 'bye' did not happen mostly by the door, again, it was in the kitchen. That's where you say good bye, then go to the door where you might, or might not, say it again.