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 optimist.
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.
