থিংক ইন ইংলিশ (হার্ডকভার)

"Language has a critical period for learning. The way to understand this Graph is to look at your age on the horizontal axis. And you'll see on the vertical your skill at acquiring a Second Language.
The babies and children are geniuses until they turn seven, and then there's a systematic decline. After puberty, we fall off the map. No scientists dispute this curve, but laboratories all over the world are trying to figure out why it works this way."