This is one of the better TED Talks I have seen to date. It is definitely worth watching!
From the abstract: MIT researcher Deb Roy wanted to understand how his infant son learned language — so he wired up his house with videocameras to catch every moment (with exceptions) of his son’s life, then parsed 90,000 hours of home video to watch “gaaaa” slowly turn into “water.” Astonishing, data-rich research with deep implications for how we learn.
For an interesting related talk, check out Patricia Kuhl– The linguistic genius of babies (TEDxRanier).