Contributor(s): Professor Cass R. Sunstein | How does social change happen? Why is it so hard to anticipate? A key reason is the existence of hidden preferences, which may or may not be unleashed. Cass R. Sunstein (@CassSunstein) is currently the Robert Walmsley University Professor at Harvard. From 2009 to 2012, he was Administrator of the White House Office of Information and Regulatory Affairs. He is the founder and director of the Program on Behavioral Economics and Public Policy at Harvard Law School. His latest book is How Change Happens. To pre-order a copy of How Change Happens, which can be collected from independent bookshop Pages of Hackney at the event, please go to How Change Happens. Paul Dolan (@profpauldolan) is Professor of Behavioural Science at the London School of Economics. He is Head of Department in Psychological and Behavioural Science and Director of the EMSc in Behavioural Science. He is author of the Sunday Times best-selling book Happiness by Design, and Hap