The New York Times investigates how the goohs and gaahs of baby babble transform through the first year of life, becoming ever more language-like until they mutate into the first recognisable words.
But more than just tracking how the sounds change over time, the piece is a fascinating look at how they become enmeshed in social interaction and alter as they start to elicit specific responses from other people.
Some of the most exciting new research [pdf], according to D. Kimbrough Oller, a professor of audiology and speech-language pathology at the University of Memphis, analyzes the sounds that babies make in the first half-year of life, when they are “squealing and growling and producing gooing sounds.” These sounds are foundations of later language, he said, and they figure in all kinds of social interactions and play between parents and babies — but they do not involve formed syllables, or anything that yet sounds like words.
“By the time you get past 6 months of age, babies begin to produce canonical babbling, well-formed syllables,” Professor Oller said. “Parents don’t treat those earlier sounds as words; when canonical syllables begin to appear, parents recognize the syllables as negotiable.” That is, when the baby says something like “ba ba ba,” the parent may see it as an attempt to name something and may propose a word in response.
Link to NYT piece on understanding babble.
pdf of chapter on Evolution of Communicative Flexibility.
Mind Hacks 
I didn’t notice the M.I.T. researcher who videotaped every moment of his baby learning to talk? It’s featured in this excellent BBC documentary “Why Do We Talk?” — watch in full here:
http://topdocumentaryfilms.com/why-do-we-talk/
Apparently, as a child, I had grasped the idea of taking turns in a conversation, but not managed any words yet – so I would sit with people, babble for a few long seconds and then stop – politely looking at them and waiting for their response. When they finished their response, I would babble again.