At a time when policy makers want to change the behaviour of citizens to tackle a broad range of social problems, such as climate change, excessive drinking, obesity and crime, a promising new policy approach has appeared that seems capable of escaping the liberal reservations typically associated with all forms of regulatory action. After having relied on the assumption that governments can only change people's behaviour through rules and regulations, policy makers now seem ready to design policies that better reflect how people really behave, not how they are assumed to behave as rational agents. The approach, which stems from the increasingly ubiquitous findings of behavioural research, is generally captured under the evocative concept of ‘nudge’. Inspired by ‘libertarian paternalism’, it suggests that the goal of public policies should be to steer citizens towards making positive decisions as individuals and for society while preserving individual choice. Acting as ‘choice architects’ policy makers organize the context, process and environment in which individuals make decisions. In so doing, they exploit some patterns of irrationality, often called ‘cognitive biases’, to manipulate people's choices. Thus, in the famous Cafeteria example, the school's management might try to affect students’ diet by rearranging the display of food to make it more likely that students will choose the healthy option. This innovative approach to policy making is part of a broader shift from traditional regulation to regulatory governance that is generally referred to as New Governance.