In many families adults speak to babies in simplified language.
Conclusion
Constantly repeating simple phrases does not provide extra help to children in learning a language.
Evidence (we know this because)
There are families in which no one speaks to babies this way, yet the children in these families master the grammatical structure of their language just as well as and as quickly as other children do.
Evaluate
There are two big problems with this argument:
The conclusion is trying to prove that "X does not help people to do Y", whereas the evidence is only going to establish that .
It's akin to this flawed argument: .
We would object to this Harvard argument and to the baby argument the same way --
This author is assuming that
The second problem with the argument is that the conclusion is about whether or not something "helps children to learn a language", whereas the evidence is about whether or not children .
The author seems to think that, But maybe repeating simple phrases is supposed to help a kid learn a language for a different reason.
Goal
Look for an answer speaking to the assumption of, .
Or look for an answer ruling out an objection, where if we negate it, it might allow us to argue that repeating simple phrases does provide extra help to children learning a language.