Kids should be spoken to as soon as they are a few months (less than 1 year) old exactly like speaking to an older child.  They may not be able to speak but they do understand the tone, and facial expressions etc.  Kids will learn the language a lot faster than 99% of parents realize, even when crying is their "language".

Didn't think it possible, but it is.  Friends have 3 kids ALL of them were spoken to in Adult language almost from birth.  By 2 years old the 2 older ones were speaking in sentences. They knew "no" really meant no, there was "negociating"  but never were they allowed to say no or not pay attention to what the parents said. The younger is under 1.5 years old and learning words, and even she knows she has to pay attention and when she misbehaves she understands there are consequences. Just as there are good consequences for good behavior.

Not once have the 3 kids have been talked to with the "goo goo,,gagga-gagga" krap.  None of the kids have ever been physically disiplined e.v.e.r !  They all know they are loved to death but are not allowed to act like heathens either.   

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