Dr Jay Giedd, guest of UNSW's 2012 Brain Sciences Symposium, is the Chief of Brain Imaging at the U.S. Institute of Mental Health and has spent more than 20 years researching the adolescent brain. He speaks with Sarah Macdonald about how the explosion of social media and other challenges of  modern society are changing the young brain, why reading isn't "natural", and why the exponential increase in violent video games is not necessarily a bad thing.