“Baby Talk” is a perfect representation of how a neurotypical child develops speech. Babbling and cooing will develop into expressive talking that is full of sentences, thoughts, emotions, but NO WORDS. Not yet.
We note that in some children with the diagnosis of a spectrum disorder, they may have skipped all the preliminary stages of speech, no babbling or “baby talk”, and suddenly produce words, even full sentences.
As an example, I had a relative who did not do any “baby talk”, a fact that made his family proud. However he withheld speech until he was three years old. His father told the family, “He doesn’t get to eat until he asks for food.” So, clever little guy that he was, he looked at his father and said his first words: “Please pass the mashed potatoes.”
Many children on the spectrum are exceedingly bright of course, and this relative was one who would have been considered on the spectrum today. He never did develop socially appropriate behaviors and was often demeaning to those around him. I believe that we can understand a lot from the way that speech emerges.