Abstract: The limitations of one-time policies in reducing food waste underscore the need for a more engaging, sequenced policy design. In this pre-registered field experiment, we test the effectiveness of a nudge with or without a thinking prompt in reducing food waste and generating financial savings, using a step-wedged design. 193 households in Fife Council, Scotland reported their food waste and grocery bills across 8 weeks (N=1081) and completed pre- and post-experiment questionnaires. The nudge group received a feedback report, and the week after, it was further encouraged to think about food waste reduction strategies (nudge+). Both interventions reduced household food waste compared to the baseline, on average. The nudge+ decreased food waste by 10g compared to the nudge, with a significant lagged effect in the post-treatment period. Planning, storage skills and disposal attitudes improved after the experiment. Policy sequencing can enhance the effectiveness of behavioural interventions in reducing food waste.

Abstract: Meat consumption and willingness to reduce it may be linked to political ideology, with a common assumption that left-leaning individuals favour meat reduction policies more than right-leaning ones. However, rigorous evidence is lacking on this point. This study examines whether support for meat reduction policies varies by self-reported political ideology. Using a conjoint experiment with nationally representative samples from Denmark, Germany, the Netherlands, and the UK (N=2,008), we randomly vary four attributes of a hypothetical meat tax: cost, revenue redistribution, motivation, and outreach. We find that right-wing voters support a baseline meat tax more than left-wing voters, but their support decreases when policies involve revenue redistribution, incorporate environmental costs, or emphasize environmental over health concerns. These patterns are partly explained by differences in Schwartz values across ideological groups. Our findings highlight the role of narratives in shaping political debates on meat taxation.

Abstract: Are stringent vaccine promotion policies associated with higher uptake, even when people are hesitant about the vaccine? In a survey of G-7 countries, 22% of respondents (n=42,217) say they do not trust the COVID-19 vaccine, but half of them nonetheless take up at least one vaccination. We investigate a range of factors associated with vaccination, focusing on the stringency of vaccine promotion policies, which change the costs and benefits of immunization choices. We show that living in a country with more stringent vaccination policies is positively associated with uptake of the initial vaccination protocol, including among people who are skeptical about the vaccine. The association between policy stringency and uptake of the booster vaccine is also positive among those who are skeptical about the vaccine. However, this association is not differentially stronger compared to the group who trust the vaccine. Our findings suggest that policy stringency can play a key role in vaccine uptake. Our findings raise questions for policymakers, in finding the appropriate balance between persuasive and coercive policies to promote policy goals.

Abstract: Understanding the mechanisms through which behavioural interventions work remains a critical challenge in behavioural science. While randomized controlled trials (RCTs) provide reliable evidence for intervention efficacy, they are seldom designed to reveal the underlying causal pathways that drive observed outcomes. We introduce a comprehensive data-driven methodological protocol -- BriDGE -- that combines advanced causal inference techniques, such as Directed Acyclic Graphs (DAGs), causal discovery algorithms, and Generalized Additive Models (GAMs), to enhance mechanistic insights in behavioural applications. BriDGE modifies conventional experimental analysis with a stepwise approach including DAG-based hypothesis formulation, modelling of nonlinear relationships with GAMs, and detailed mediation analysis. Using bootstrapping and sensitivity checks, BriDGE ensures robust and reliable detection of both direct and indirect effects. We use a simulation study to validate BriDGE's ability to identify complex causal mechanisms, offering researchers with a robust framework for deepening understanding of causal mechanisms and optimizing intervention design. There are natural limitations of BriDGE -- we discuss their implications when applied to public policy. We call for a greater integration of these methods in the toolkit of applied policy analysis to bridge the gap from “what works" to “why and how it works".

Abstract: Food policy often struggles to reach diverse population groups, and well-intentioned interventions can sometimes exacerbate inequalities along socio-demographic groups. This systematic review examines whether default nudges in food choices have consistent effects across different socio-demographic groups, or whether their impact varies depending on factors such as education level, age, and gender. Using primary data from 12 studies (N = 40 interaction effects), we analyzed how age, gender, and education moderate the effectiveness of defaults compared to active choice conditions. Results show no consistent and rarely any interaction effects, suggesting defaults influence food decisions similarly across socio-demographic groups. A possible exception is that harmful defaults may be more effective among less educated individuals. These findings highlight default nudges as a broadly equitable behavioral tool in food policy design.

Abstract: Vegetarian diets can reduce global ecological costs. Yet meat continues to be culturally dominant, especially in the West. Does culture hamper the adoption of vegetarian diets? In an online experiment, we observed the intentions of 2,775 English participants to choose vegetarian food. We causally test if framing food options with culturally familiar names alters the effectiveness of a nudge promoting vegetarianism. Facing culturally familiar food does not change the effect of the nudge. However, exploratory analyses reveal that participants ask for lower monetary compensation for being forced to choose vegetarian food when it is culturally framed. Thus, welfare losses of hard policies, like bans, may be lower when alternative options look familiar.

Abstract: Behavioural nudges, such as defaults, improve human welfare by reducing choice overload. But how far should policy-makers go in reducing available choices?  Using a preregistered, online survey experiment, we randomly assign 1,518 UK citizens to two versions of the same opt-out default nudge aimed at encouraging charitable donations. In one version, the default was embedded in a list of multiple options, whereas in the other it was presented as a single choice. In both versions, participants could opt-out and choose any preferred donation amount. We find that when the default is embedded in a multiple-choice list, opting out rates and average individual donations are significantly higher compared to the standard single-choice default. Our findings suggest that encouraging active choosing alongside a default can improve agency without necessarily deteriorating behavioural outcomes.

Abstract: Respondents from around the world are financially incentivized to complete surveys in higher paying markets, and some respondents are even willing to falsify their credentials to do so. We propose a new cost-free method for identifying and excluding non-target respondents who see blank JavaScript-programmed experiments due to VPN usage. Using a dataset of 72,200 respondents in the G-7 countries, we show that 94 respondents (0.13\%) in our entire G-7 sample and 49 respondents (0.49\%) who report being from the United States are likely using virtual private networks (VPNs) to disguise their locations to qualify for surveys outside of their country. These non-target respondents provide low-quality responses, affecting external validity. Simple JavaScript programming can reject this rare type of non-target respondent from surveys administered using Qualtrics. 

Nudge+. Think, before you nudge (under contract with Palgrave Macmillan, forthcoming in January 2026). Joint with Peter John.

Behavioural Environmental Economics and Policy (under contract with Routledge, forthcoming in December 2026). Joint with Lory Barile.