What's really going on in a teenager's brain: "These scientists have discovered that the brain goes through massive refinement in adolescence. Paths are smoothed, bridges built and rubbish cleared. As one of the American scientists interviewed by Barbara Strauch puts it, in the cheerful style shared by all of them: 'The brain's pruned back to the essentials, you know, like one of those poems, a haiku. It's as if the brain says, hey, it's time to specialise.' To enable this, there is a surge of grey matter aptly called an 'exuberance'. This overload of capacity and possibility is why teenagers can read a Russian novel a day, hack into military software, steal a car or want to save the world. It also causes a heightening of experience and emotion for which they are not fully equipped - like a rollercoaster setting off before every nut and bolt is in place".