Michael Mosley explores the latest science about how our personalities are created - and whether they can be changed. Despite appearances, Mosley is a pessimist who constantly frets about the future. He wants to worry less and become more of an opti... (more)mist. He tries out two techniques to change this aspect of his personality - with surprising results. And he travels to the frontiers of genetics and neuroscience to find out about the forces that shape all our personalities.