'A pathbreaking book that for the first time brings smart policy insights into contact with creative, rigorous testing. This book sets the standard for all future scientific evaluations of "what works".' Donald P. Green, Burgess Professor of Political Science, Columbia University 'Nudge, nudge, think, think not only informs the reader about how nudge and think strategies can be combined, but also about what the potential benefits and drawbacks of such strategies are for a range of public behaviours.' Sander van der Linden, Director, Cambridge Social Decision-Making Laboratory How can governments persuade their citizens to act in socially beneficial ways? This book builds on the idea of 'light touch interventions' or 'nudges' proposed in Richard Thaler and Cass Sunstein's highly influential Nudge (2008). While recognising the power of this approach, it argues that an alternative also needs to be considered: a 'think' strategy that calls on citizens to decide their own priorities as part of a process of civic and democratic renewal. As well as setting out these divergent approaches in theory, the book provides evidence from a number of large-scale experiments to show how using 'nudge' or 'think' techniques works in practice. Updated and rewritten, this second edition features a new epilogue that reflects on recent developments in nudge theory and practice, introducing a radical version of nudge, 'nudge plus'. There is a substantial prologue by Cass Sunstein.