A poor child is likely to hear millions fewer words at home than a child from a professional family. And the disparity matters. An idea that is creeping into policy debate is that the key to early learning is talking–specifically, a child’s exposure to language spoken by parents and caretakers from birth to age 3, the more the better. 

Link: http://opinionator.blogs.nytimes.com/2013/04/10/the-power-of-talking-to-your-baby/