Interventions aimed to change behavior (so called nudges) are becoming more and more popular among policymakers. However, in order to be able to effectively use nudges, it is important to understand when and why people find them acceptable. The objective of this thesis is therefore to improve the understanding of when nudges are judged to be acceptable. The thesis focuses on a model for behavioral change. The model contains two parts, nudge technique and acceptance of nudges. Nudge technique refers to how the nudge is designed to function in regard to psychological mechanism and functionality.

The nudge technique part of the model is expanded and problematized from an ethical perspective in the first part of this thesis, by exemplifying psychological mechanisms behind different techniques and explaining why they might be intrusive to individuals’ freedom of choice. In the second part of this thesis it is discussed why acceptance is an important component of making nudging legitimate and effective. This is followed by a discussion of how acceptance is empirically measured. The empirical part of the thesis is based on four papers which all use a quantitative online survey approach to study the judgements of nudges from the general public.

Paper 1 was a first attempt to measure whether nudges which are common in the nudge literature are acceptable interventions according to the general public. We found that the nudges that were categorized as pro-self were more likely to be rated as acceptable and less likely to be perceived as intrusive to freedom of choice compared to pro-social nudges. Furthermore, the effect of decision styles and worldview on acceptance was explored. In paper 2, we explored whether the difference between acceptance found for pro-social nudges and proself nudges could be increased by framing nudges as beneficial for society or individuals. The framing had no effect on acceptance but, as in paper 1, pro-social nudges were found to be more intrusive to freedom of choice compared to pro-self framed nudges. Moreover, different nudge techniques had different rates of acceptance even with the same explicit goal for the nudges. In paper 3, we examined whether the alternative to nudges affects the perceived acceptability and intrusiveness of default-changing nudge techniques. The alternatives given to the nudges were either to enforce the intended behavioral change with legislation or to do nothing at all in order to change the behavior. We find no difference in aggregated acceptance, however, the judgements vary depending on individuals’ worldview. Paper 4 explored if the choice architect’s (the creator/proposer of the nudge) political affiliation affects acceptance rating for proposed nudge interventions and legislation. We find that acceptance of both nudges and legislation increases with the level of matching between people’s political orientation and the choice architect’s political affiliation.

Taken together, the findings suggest that there is more to creating an acceptable nudge than to merely take a nudge technique that was acceptable in one context and apply it in another. Moreover, nudges that are rated as more beneficial towards individuals compared to society at large are in general more likely to be found acceptable and less intrusive to freedom of choice. It is important to have knowledge about the target population (e.g. their decision styles, world-views, and political orientation) to avoid backfires when implementing nudges.