Material World - 22/02/2007

Ever heard a joke that you don't understand but you laugh anyway just because everyone else is? Why is laughter so contagious? Quentin Cooper talks to neuroscientist Professor Sophie Scott, from University College London, about her research on the brain cells that determine why when we hear laughter, we feel compelled to join in. Robin Dunbar, from the University of Liverpool, explains why laughter is essential for social bonding and why if you want to collect money for a charity, do it at a comedy club.