In Nudge (2008) Richard Thaler and Cass Sunstein suggested that public policy–makers arrange decision–making contexts in ways to promote behaviour change in the interest of individual citizens as well as that of society. However, in the public sphere and Academia alike widespread discussions have appeared concerning the public acceptability of nudgebased behavioural policy. Thaler and Sunstein's own position is that the anti–nudge position is a literal non–starter, because citizens are always influenced by the decision making context anyway, and nudging is liberty preserving and acceptable if guided by Libertarian Paternalism and Rawls’ publicity principle. A persistent and central tenet in the criticism disputing the acceptability of the approach is that nudging works by manipulating citizens’ choices. In this paper, we argue that both lines of argumentation are seriously flawed. We show how the anti–nudge position is not a literal non–starter due to the responsibilities that accrue on policy–makers by the intentional intervention in citizens’ life, how nudging is not essentially liberty preserving and why the approach is not necessarily acceptable even if satisfying Rawls’ publicity principle. We then use the psychological dual process theory underlying the approach as well as an epistemic transparency criterion identified by Thaler and Sunstein themselves to show that nudging is not necessarily about “manipulation”, nor necessarily about influencing “choice”. The result is a framework identifying four types of nudges that may be used to provide a central component for more nuanced normative considerations as well as a basis for policy recommendations.

In recent years the concepts of ‘nudge’ and ‘libertarian paternalism’ have become popular theoretical as well as practical concepts inside as well as outside academia. But in spite of the widespread interest, confusion reigns as to what exactly is to be regarded as a nudge and how the underlying approach to behaviour change relates to libertarian paternalism. This article sets out to improve the clarity and value of the definition of nudge by reconciling it with its theoretical foundations in behavioural economics. In doing so it not only explicates the relationship between nudges and libertarian paternalism, but also clarifies how nudges relate to incentives and information, and may even be consistent with the removal of certain types of choices. In the end we are left with a revised definition of the concept of nudge that allows for consistently categorising behaviour change interventions as such and that places them relative to libertarian paternalism.

In recent years, the nudge approach to behavior change has emerged from the behavioral sciences to challenge the traditional use of regulation in public health strategies to address modifiable individual-level behaviors related to the rise of noncommunicable diseases and their treatment. However, integration and testing of the nudge approach as part of more comprehensive public health strategies aimed at making healthy choices easier are being threatened by inadequate understandings of its scientific character, its relationship with regulation, and its ethical implications. This article reviews this character and its ethical implication with a special emphasis on the compatibility of nudging with traditional regulation, special domains of experience, and the need for a more nuanced approach to the ethical debate. The aim is to advance readers' understanding and give guidance to those who have considered working with or incorporating the nudge approach into programs or policies aimed at making healthful choices easier.

Background This study investigates a simple, generic and easily scalable nudge to promote healthy and sustainable food choices at conferences by using a vegetarian lunch-default as a normative signal. Methods At three conferences, participants registering electronically were randomized into two groups: Group 1 received a standard lunch registration presenting a non-vegetarian buffet as the default, but allowing the active choice of a vegetarian option; Group 2 received a registration presenting a vegetarian buffet as the default, allowing the active choice of a non-vegetarian option. The study also assessed gender differences for two of the conferences and the participants’ acceptance of the nudge at one of the conferences. Results In experiment A the vegetarian choice increased from 2% to 87% (N = 108, P < 0.001). In experiment B it increased from 6% to 86% (N = 112, P < 0.001). In experiment C it increased from 12.5% to 89% (N = 110, P < 0.001). A significant tendency for men, but not women, to opt out of the vegetarian default was found and a clear majority of participants reported positive attitudes toward the nudge. Conclusions Changing the lunch-default to a vegetarian option is an effective, generic, easy to scale and well-accepted nudge to promote healthy and sustainable food choices at conferences.