Citizen approval of nudging interventions promoting healthy eating: the role of intrusiveness and trustworthiness

Effectiveness of visual nudges for encouraging healthier beverage choices from vending machines

ISSUES ADDRESSED

Research suggests visual nudging techniques can subtly encourage healthier consumption. Two experiments explored the effect of four visual primes for nudging drink choices from a vending machine display.

METHODS

Participants (17-25 years) were randomly assigned to view vending machine advertising posters containing pictorial nudges of water, soft drink, general health (runner), or a text-only control, for nudging vending machine choices. Participants then selected an item from a vending machine display containing drinks only (Experiment 1; n = 164), or both drinks and snack foods (Experiment 2, n = 684).

RESULTS

In both experiments, nudging condition predicted beverage choice. Specifically, the water image nudged healthier beverage choices in both experiments. However, there was no effect on food choice in Experiment 2. Furthermore, in both experiments, liking and habitual consumption of chosen items were also significant predictors of choice, but condition predicted beverage choice over and above these.

CONCLUSION

A water prime may be an effective means of encouraging healthier beverage choices in a vending machine environment. SO WHAT?: Findings have the potential to inform strategies for encouraging healthier beverage choices from vending machine environments.

Nudging towards sustainable dining: Exploring menu nudges to promote vegetarian meal choices in restaurants

Food choice behavior plays a large role in achieving sustainability goals. Meat in particular has a negative environmental impact as compared with plant-based food - and is more frequently chosen in restaurant contexts. To increase plant-based meal choices in restaurants, we tested three nudges for menus that are likely to be implemented by restaurant owners: a hedonic label (e.g., artisanal vegetable burger), a chef's recommendation (specifying the vegetarian option as the chef's favorite), and a salience nudge (a box around the vegetarian option). In an online experiment, we showed participants (n = 513) in four conditions (no nudge, hedonic label, chef's recommendation, and salience nudge) five menus with four meal options each, one of which was vegetarian. We asked participants to choose a meal and subsequently to rate these meals on how tasty and indulgent they were (taste and indulgence attributions). We then revealed which nudge was used to the participants and asked how participants received it. Results show that the hedonic label and chef's recommendation nudge (but not the salience nudge) both increase vegetarian meal choices. The hedonic label increased participants' attributions of indulgence of the meal, but not of tastiness. This finding fits with restaurants' gastronomic, pleasure-seeking context and shapes future directions of labeling interventions, namely that indulgence attributions can be increased in vegetarian foods. Furthermore, the nudges were generally well accepted and participants' intention to return to the (virtual) restaurant was high. Finally, customers expected the hedonic label nudge to be more effective in promoting vegetarian food choices than the other two nudges, partially corresponding with our findings of actual effectiveness.

Exploring the Viability and Acceptance of Nudge in Public Policies for Health Promotion

BACKGROUND

Behaviorally informed interventions, such as nudging, encourage actions intended to promote longer and healthier lives. Holding significant potential for influencing health policies and healthcare practices, these interventions are partaking of a shift in governance and public health policymaking. However, a substantial knowledge gap remains regarding the feasibility and appropriateness of implementing policies that draw on nudge.

METHODS

Ae survey on nudge's acceptability) was adapted to the Portuguese context to access attitudes towards 16 nudge measures. The research focused on evaluating attitudes among political science and public administration BSc and MSc students from nine Portuguese universities, and analyzing the relationship between these attitudes, sociodemographic characteristics, and sociopolitical attitudes. The data analysis involved the application of descriptive and inferential statistics.

RESULTS

The participants exhibited a moderate-to-high level of approval for various nudge measures, particularly those related to nutrition and public education/awareness raising. The study identified a nuanced relationship between the level of intrusiveness of nudges and their public approval, indicating that interventions preserving the architecture of choice gathered higher acceptance compared to more intrusive approaches. Notably, approval was associated with a high level of trust in social groups and a low propensity for risk-taking and alcohol consumption.

CONCLUSIONS

This study not only sheds light on the types of nudge measures that are likely to be more acceptable for promoting healthy behaviors, but also establishes a crucial link between behavioral interventions and healthcare policies. Understanding the nuanced factors influencing the public acceptance of nudges contributes to the discourse on the implementation of behaviorally informed health policies and emphasizes the importance of tailoring interventions to align with public values and preferences.

When and Why Do People Accept Public-Policy Interventions? An Integrative Public-Policy-Acceptance Framework

The successful introduction of public policies to prompt behavior change hinges on the degree to which citizens endorse the proposed policies. Although there is a large body of research on psychological determinants of public policy acceptance, these determinants have not yet been synthesized into an integrative framework that proposes hypotheses about their interplay. In this article, we develop a review-based, integrative public-policy-acceptance framework that introduces the desire for governmental support as a motivational foundation in public-policy acceptance. The framework traces the route from problem awareness to policy acceptance and, ultimately, policy compliance. We propose this relationship to be mediated by a desire for governmental support. We integrate numerous key variables assumed to qualify the relationship between problem awareness and the desire for governmental support, such as control attributions, trust, and value fit, as well as the relationship between the desire for governmental support and policy acceptance, such as perceived policy effectiveness, intrusiveness, and fairness. We exemplify the use of the proposed framework by applying it to climate policies.

Acceptability of workplace choice architecture modification for healthy behaviours

BACKGROUND

Altering the choice architecture of decision contexts can assist behaviour change, but the acceptability of this approach has sparked debate. Considering hypothetical interventions, people generally welcome the approach for promoting health, but little evidence exists on acceptance in the real world. Furthermore, research has yet to explore the implementers' perspective, acknowledging the multidimensionality of the acceptability construct. Addressing these knowledge gaps, this study evaluated the acceptability of a quasi-experimental implementation-effectiveness trial that modified the worksite choice architecture for healthy eating and daily physical activity.

METHODS

Fifty-three worksites participated in the 12-month intervention and implemented altogether 23 choice architecture strategies (Mdn 3/site), including point-of-choice prompts and changes to choice availability or accessibility. Retrospective acceptability evaluation built on deductive qualitative content analysis of implementer interviews (n = 65) and quantitative analysis of an employee questionnaire (n = 1124). Qualitative analysis examined implementers' thoughts and observations of the intervention and its implementation, considering six domains of the Theoretical Framework of Acceptability: ethicality, affective attitude, burden, intervention coherence, opportunity costs, and perceived effectiveness. Quantitative analysis examined employees' acceptance (7-point Likert scale) of eight specific intervention strategies using Friedman test and mixed-effects logistic regression.

RESULTS

Implementers considered the choice architecture approach ethical for workplace health promotion, reported mostly positive affective attitudes to and little burden because of the intervention. Intervention coherence supported acceptance through increased interest in implementation, whereas low perceived utility and high intensity of implementation reduced cost acceptance. Perceived effectiveness was mixed and varied along factors related to the implementer, social/physical work environment, employer, and employee. Employees showed overall high acceptance of evaluated strategies (Mdn 7, IQR 6.4-7), though strategies replacing unhealthy foods with healthier alternatives appeared less supported than providing information or enhancing healthy option availability or accessibility (p-values < 0.02). Greater proportion of male employees per site predicted lower overall acceptance (OR 4.4, 95% CI 1.2-16.5).

CONCLUSIONS

Work communities appear to approve workplace choice architecture interventions for healthy eating and physical activity, but numerous factors influence acceptance and warrant consideration in future interventions. The study contributes with a theory-based, multidimensional evaluation that considered the perspectives of implementers and influenced individuals across heterogeneous real-world settings.

Perception of nudge interventions to mitigate medication errors risk in healthcare service delivery

BACKGROUND

Conventional cognitive interventions to reduce medication errors have been found to be less effective as behavioural change does not always follow intention change. Nudge interventions, which subtly steer one's choices, have recently been introduced.

METHODS

Conducted from February to May 2023, this study aimed to determine the relationships between perceived effectiveness and perceived ease of implementation of six nudge interventions to reduce medication errors, i.e., provider champion, provider's commitment, peer comparison, provider education, patient education and departmental feedback, and the moderating effects of seniority of job positions and clinical experience on nudge acceptability. Partial Least Square Structural Equation Modelling was used for data analysis.

RESULTS AND DISCUSSION

All six nudge strategies had significant positive relationships between perceived effectiveness and acceptability. In three out of six interventions, perceived ease of implementation was shown to have positive relationships with perceived acceptability. Only seniority of job position had a significant moderating effect on perceived ease of implementation in peer comparison intervention. Interventions that personally involve senior doctors appeared to have higher predictive accuracy than those that do not, indicating that high power-distance culture influence intervention acceptability.

CONCLUSION

For successful nudge implementations, both intrinsic properties of the interventions and the broader sociocultural context is necessary.

Campus food service users' support for nudge strategies for fruit and vegetable-rich items: findings from a large Canadian national sample

Although customer support is critical to the wider uptake of nudging strategies to promote fruits and vegetables (FV) in institutional food service (FS) settings, empirical research is sparse and typically based on small convenience samples. An online survey was conducted to assess support, perceived effectiveness and intrusiveness of nine nudge types drawn from Münscher et al.'s Taxonomy of Choice Architecture. We focused on the setting of campus FSs across Canada. A national sample of post-secondary students regularly using campus FSs was used (N 1057). Support for changing the range of options (B3) was the highest, closely followed by changing option-related effort (B2) and changing option-related consequences (B4). Facilitating commitment (C2), changing default (B1) and providing a social reference point (A3) received lowest support. Furthermore, we extracted three clusters of respondents based on perceived effectiveness and intrusiveness of nudge types. Characterised by a relatively low level of perceived effectiveness and moderately high level of intrusiveness, Cluster 1 (61⋅7 % of the sample) reported the lowest support for nudges. Cluster 2 (26⋅6 %), characterised by intermediate effectiveness and low intrusiveness of nudging, reported a high level of support for nudges. Lastly, Cluster 3 (11⋅7 %), characterised by high perceived effectiveness of as well as high perceived intrusiveness, reported the highest level of support for nudges. Findings confirm overall support for FV nudging, with significant differences across nudge types. Differences in customers' acceptance and perception across nudge types offer campus FS operators initial priors in selecting nudges to promote FV.

Nudging Interventions on Alcohol and Tobacco Consumption in Adults: A Scoping Review of the Literature

Background: The World Health Organization identified alcohol and tobacco consumption as the risk factors with a greater attributable burden and number of deaths related to non-communicable diseases. A promising technique aimed to modify behavioral risk factors by redesigning the elements influencing the choice of people is nudging. Methodology: A scoping review of the literature was performed to map the literature evidence investigating the use of nudging for tobacco and alcohol consumption prevention and/or control in adults. Results: A total of 20 studies were included. The identified nudging categories were increasing salience of information or incentives (IS), default choices (DF), and providing feedback (PF). Almost three-quarters of the studies implementing IS and half of those implementing PF reported a success. Three-quarters of the studies using IS in conjunction with other interventions reported a success whereas more than half of the those with IS alone reported a success. The PF strategy performed better in multi-component interventions targeting alcohol consumption. Only one DF mono-component study addressing alcohol consumption reported a success. Conclusions: To achieve a higher impact, nudging should be integrated into comprehensive prevention policy frameworks, with dedicated education sessions for health professionals. In conclusion, nudge strategies for tobacco and alcohol consumption prevention in adults show promising results. Further research is needed to investigate the use of nudge strategies in socio-economically diverse groups and in young populations.

Instagram-based priming to nudge drink choices: Subtlety is not the answer

Instagram-based priming (e.g., subtly incorporating healthy drinks into the background of Instagram images) could potentially nudge healthier consumption behaviours. Given the negative health consequences associated with sugar-sweetened-beverage consumption, two experiments tested the effect of three sets of Instagram-based primes for nudging drink choices from a visual food and drinks display. Participants (18-25 years) were randomly assigned to view a series of Instagram advertising images (for technology, travel, or homeware products) that included a glass containing water (water prime) or cola (soft drink prime), or no drink (control). They then selected an item from the visual display containing snack foods and drinks. In Experiment 1 (n = 493) beverages were subtly incorporated into the priming images; in Experiment 2 (n = 471) beverages were made more prominent. Priming condition did not predict choice in Experiment 1 but did so in Experiment 2, where participants in the soft drink prime condition were significantly more likely to select a drink versus a food, compared to those in the water prime and control conditions. The water prime did not predict choice in either study. A greater percentage of participants noticed the beverage primes in Experiment 2 than in Experiment 1. Overall, it appears that when clearly visible, soft drinks incorporated into Instagram-style images can nudge drink choices. However, a less subtle approach may be needed to effectively encourage healthier drink choices.

Primary care professionals' support for Covid-19 vaccination mandates: Findings from a US national survey

Healthcare organizations have been early adopters of Covid-19 vaccine mandates as a strategy to end the pandemic. We sought to evaluate support for such mandates among pediatric primary care professionals (PCPs) in the United States. In February-March 2021, we conducted a national online survey of 1,047 PCPs (71% physicians). We used multivariable logistic regression to assess correlates of PCPs' support for Covid-19 vaccine mandates for health care workers. Most PCPs supported Covid-19 vaccine mandates for health care workers (83%). PCPs were more likely to support mandates if they perceived health care workers to be at highest risk of getting Covid-19 compared to other worker types (8 percentage points, p < 0.01). PCPs were also more likely to support mandates if their clinic recommended or required vaccination (11 percentage points and 20 percentage points respectively, both p < 0.01). However, PCPs were less likely to support mandates if their clinic offered incentives to vaccinate (10 percentage points, p < 0.05). Clinic recommendations and requirements for Covid-19 vaccination may increase support for mandates. Incentives may decrease support, perhaps by creating the perception that viable alternatives to mandates exist.

Acceptance of healthy lifestyle nudges in the general population of Singapore

Background

In recent years, behaviourally driven policies such as nudges have been increasingly implemented to steer desired outcomes in public health. This study examines the different nudges and the socio-demographic characteristics and lifestyle behaviours that are associated with public acceptance of lifestyle nudges.

Methods

The study used data from the nationwide Knowledge, Attitudes and Practices study (KAP) on diabetes in Singapore. Three types of nudges arranged in increasing order of intrusiveness were examined: (1) information government campaigns, (2) government mandated information and (3) default rules and choice architecture. Acceptance was assessed based upon how much respondents ‘agreed’ with related statements describing heathy lifestyle nudges. Multivariable linear regressions were performed with socio-demographics and lifestyle behaviours using scores calculated for each nudge.

Results

The percentage of respondents who agreed to all statements related to each nudge were: 75.9% (information government campaigns), 73.0% (government mandated information), and 33.4% (default rules and choice architecture). Respondents of Malay/Others ethnicity (vs. Chinese) were more likely to accept information government campaigns. Respondents who were 18 – 34 years old (vs 65 years and above), female, of Malay/Indian ethnicity (vs Chinese), were sufficiently physically active, and with a healthier diet based on the DASH (Dietary Approach to Stop Hypertension) score were more likely to accept nudges related to government mandated information. Respondents of Malay/Indian ethnicity (vs Chinese), and who had a healthier diet were more likely to accept default rules and choice architecture.

Conclusion

Individuals prefer less intrusive approaches for promoting healthy lifestyle. Ethnicity and lifestyle behaviours are associated with acceptance of nudges and should be taken into consideration during the formulation and implementation of behaviourally informed health policies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13668-x.

Customer support for nudge strategies to promote fruit and vegetable intake in a university food service

Background

Diverse nudges, also known as choice architectural techniques, have been found to increase fruit and vegetable (FV) selection in both lab and field studies. Such strategies are unlikely to be adopted in mass eating settings without clear evidence of customer support; confirmation in specific contexts is needed. Inspired by the Taxonomy of Choice Architecture, we assessed support for eight types of nudging to increase the choice of FV-rich foods in a university food service. We also explored whether and to what extent nudge support was associated with perceived effectiveness and intrusiveness.

Methods

An online survey was conducted with students who used on-campus cafeterias. Multiple recruitment methods were used. Participants were given 20 specific scenarios for increasing FV selection and asked about their personal support for each nudge, as well as perceived intrusiveness and effectiveness. General beliefs about healthy eating and nudging were also measured. Results were assessed by repeated measures ANOVA for the 8 nudge types.

Results

All nudge scenarios achieved overall favourable ratings, with significant differences among different types of nudging by the 298 respondents. Changing range of options (type B3) and changing option-related consequences (type B4) received the highest support, followed by changing option-related effort (type B2) and making information visible (type A2). Translating information (type A1), changing defaults (type B1) and providing reminders or facilitating commitment (type C) were less popular types of nudging. Providing social reference points (type A3) was least supported. Support for nudge types was positively associated with the belief that food services have a role in promoting healthy eating, perceived importance of FV intake, trustworthiness of the choice architect and female gender. Lastly, support for all types of nudges was positively predicted by perceived effectiveness of each nudge and negatively predicted by perceived intrusiveness above and beyond the contribution of general beliefs about healthy eating and nudging.

Conclusions

Findings from the current study indicate significant differences in support for nudge techniques intended to increase FV selection among university cafeteria users. These findings offer practical implications for food service operators as well as public health researchers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13054-7.

Nudging physical distancing behaviors during the pandemic: a field experiment on passengers in the subway stations of shiraz, Iran

Background

The possibility of the emergence of new pandemics necessitates further research into using simple strategies to promote social distancing behaviors in public. Most of the current evidence on effectiveness of physical distancing interventions is based on self-report and measure of intention which will not necessarily predict actual behavior.

Methods

A field experimental study was conducted in the subway stations of Shiraz, Southern Iran. The interventions were based on intuitions from protection motivation theory and consisted of using environmental nudges to notify the passengers of the pandemic situation (threat appeal) and a verbal advice on keeping a safe physical distance as an effective method of protection against COVID-19 (coping message). Average physical distancing was estimated as the number of steps between two consecutive passengers and was compared between interventions (n = 1045) and the control (n = 855) groups.

Results

A total of 1900 people riding on subway escalators were directly observed during two intervention conditions and the control condition. Under either threat or coping-based interventions, passengers were two times more likely (OR 2.0, 95%CI 1.5–2.7, P <  0.001) to keep a physical distance of at least 1.2 m from the traveler in front compared with those who did receive no intervention. The Kruskal-Wallis test revealed that there was a significant improvement in physical distancing behaviors with coping advice compared with threat appeal and the control conditions (χ2 = 120.84, df = 2, p <  0.001).

Conclusions

Our findings suggest that simple and inexpensive theory-based interventions can be used in crowded public spaces to promote physical distancing within the context of the pandemic.

Nudgeability: Mapping Conditions of Susceptibility to Nudge Influence

Nudges are behavioral interventions to subtly steer citizens' choices toward "desirable" options. An important topic of debate concerns the legitimacy of nudging as a policy instrument, and there is a focus on issues relating to nudge transparency, the role of preexisting preferences people may have, and the premise that nudges primarily affect people when they are in "irrational" modes of thinking. Empirical insights into how these factors affect the extent to which people are susceptible to nudge influence (i.e., "nudgeable") are lacking in the debate. This article introduces the new concept of nudgeability and makes a first attempt to synthesize the evidence on when people are responsive to nudges. We find that nudge effects do not hinge on transparency or modes of thinking but that personal preferences moderate effects such that people cannot be nudged into something they do not want. We conclude that, in view of these findings, concerns about nudging legitimacy should be softened and that future research should attend to these and other conditions of nudgeability.

Digital Nudging for Online Food Choices

When people search for what to cook for the day, they increasingly use online recipe sites to find inspiration. Such recipe sites often show popular recipes to make it easier to find a suitable choice. However, these popular recipes are not always the healthiest options and can promote an unhealthy lifestyle. Our goal is to understand to what extent it is possible to steer the food selection of people through digital nudging. While nudges have been shown to affect humans' behavior regarding food choices in the physical world, there is little research on the impact of nudges on online food choices. Specifically, it is unclear how different nudges impact (i) the behavior of people, (ii) the time they need to make a decision, and (iii) their satisfaction and confidence with their selection. We investigate the effects of highlighting, defaults, social information, and warnings on the decision-making of online users through two consecutive user studies. Our results show that a hybrid nudge, which both involves setting a default and adding social information, significantly increases the likelihood that a nudged item is selected. Moreover, it may help decreasing the required decision time for participants while having no negative effects on the participant's satisfaction and confidence. Overall, our work provides evidence that nudges can be effective in this domain, but also that the type of a digital nudge matters. Therefore, different nudges should be evaluated in practical applications.

Who accepts nudges? nudge acceptability from a self-regulation perspective

BACKGROUND

Public acceptability of nudging is receiving increasingly more attention, but studies remain limited to evaluations of aspects of the nudge itself or (inferred intentions) of the nudger. Yet, it is important to investigate which individuals are likely to accept nudges, as those who are supposed to benefit from the implementation should not oppose it. The main objective of this study was to integrate research on self-regulation and nudging, and to examine acceptability of nudges as a function of self-regulation capacity and motivation.

METHOD

Participants (N = 301) filled in questionnaires about several components of self-regulation capacity (self-control, proactive coping competence, self-efficacy, perceived control and perceived difficulty) and motivation (autonomous motivation and controlled motivation). To evaluate nudge acceptability, we used three vignettes describing three types of nudges (default, portion size, and rearrangement) that stimulated either a pro-self behavior (healthy eating) or pro-social behavior (sustainable eating) and asked participants to rate the nudges on (aspects of) acceptability.

RESULTS

Results revealed that there were substantial differences in acceptability between the three types of nudges, such that the default nudge was seen as less acceptable and the rearrangement nudge as most acceptable. The behavior that was stimulated did not affect acceptability, even though the nudges that targeted healthy eating were seen as more pro-self than the nudges targeting sustainable eating. From all self-regulation components, autonomous motivation was the only measure that was consistently associated with nudge acceptability across the three nudges. For self-regulatory capacity, only some elements were occasionally related to acceptability for some nudges.

CONCLUSION

The current study thus shows that people are more inclined to accept nudges that target behaviors that they are autonomously motivated for, while people do not meaningfully base their judgments of acceptability on self-regulatory capacity.

What do Germans really think about health-nudges?

BACKGROUND

In recent years, policymakers have increasingly used behaviourally informed policies, including 'nudges'. They have been implemented to produce desirable social outcomes such as healthier eating and physical activity. In Germany, a small research team at the Federal Chancellery acts as the central unit to promote the introduction of nudges in the design of public life. Despite this, the nudging concept itself as well as the understanding around it has not spread widely among German citizens. When reporting about the concept, German media is often very critical of the concept.

METHODS

Using a for age, sex and educational level nationally representative online survey with 1000 participants, we investigate whether German citizens know about the concept of nudging. We also explore if they approve of the theoretical concept as well as a list of seven specific interventions regarding healthy eating and physical activity. A particular focus is placed on whether the level of approval is dependent on the target group of the intervention, as well as different intervention-initiators.

RESULTS

We find that nearly 80% of the respondents have never heard of nudging. However when being provided with a definition, we find that a strong majority (90%) supports the concept of nudging as well as all the specific interventions. Acceptance rates are higher if interventions are targeted at the general population compared to only children. All initiators - statutory health insurers, the government, private companies, and independent experts - are accepted as nudge initiators.

CONCLUSION

Amongst Germans nudges are an accepted method to promote health behaviours. Policy makers from various fields in Germany should take that into account to improve future health policy.

A nudge in the right direction: the role of food choice architecture in changing populations' diets

Populations' diets typically fall short of recommendations. The implication of this on ill health and quality of life is well established, as are the subsequent health care costs. An area of growing interest within public health nutrition is food choice architecture; how a food choice is framed and its influence on subsequent food selection. In particular, there is an appeal to manipulating the choice architecture in order to nudge individuals' food choice. This review outlines the current understanding of food choice architecture, theoretical background to nudging and the evidence on the effectiveness of nudge strategies, as well as their design and implementation. Interventions emphasising the role of nudge strategies have investigated changes to the accessibility, availability and presentation of food and the use of prompts. Empirical studies have been conducted in laboratories, online and in real-world food settings, and with different populations. Evidence on the effectiveness of nudge strategies in shifting food choice is encouraging. Underpinning mechanisms, not yet fully explicated, are proposed to relate to salience, social norms and the principle of least effort. Emerging evidence points to areas for development including the effectiveness of choice architecture interventions with different and diverse populations, and the combined effect of multiple nudges. This, alongside further examination of theoretical mechanisms and guidance to engage and inspire across the breadth of food provision, is critical. In this way, the potential of choice architecture to effect meaningful change in populations' diets will be realised.

The effects of nudging and pricing on healthy food purchasing behavior in a virtual supermarket setting: a randomized experiment

BACKGROUND

Evidence on what strategies - or combination of strategies - are most effective and equitable in promoting healthier diets is needed. This study examined the efficacy of nudging and pricing strategies on increasing healthy food purchases and the potential differential effect by socio-economic position (SEP) among Dutch adults in a virtual supermarket.

METHODS

A randomized study design was conducted within a virtual supermarket (SN VirtuMart). Participants were exposed to five within-subject study conditions (control, nudging, pricing, price salience and price salience with nudging) and randomized to one of three between-subject study arms (a 25% price increase on unhealthy products, a 25% discount on healthy products, or a 25% price increase and discount). In total, 455 participants of low and high SEP (using either education or income as proxy) were randomized to conduct their weekly shopping in a virtual supermarket for five consecutive weeks. The primary outcome included the percentage of healthy purchases. Data were analyzed using linear mixed models.

RESULTS

In total, 346 (76%) adults completed all five shops within the SN VirtuMart. Median age was 32.5, 49.2% had high education and 32.8% had high income. Out of the 12 conditions, four conditions were statistically significantly different from the control condition. Nudging and non-salient pricing strategies alone did not statistically significantly increase healthy food purchases, whereas a combination of salient price increases and discounts led to an increase in the percentage of healthy food purchases (B 4.5, 95%CI 2.6; 6.4). Combining salient pricing and nudging strategies led to increases in the percentage of healthy products in all three pricing arms, with largest effects found in the combined price increase and discount arm (B = 4.0, 95%CI = 2.0; 6.0). Effects were not modified by SEP.

CONCLUSIONS

Combining health-related price increases and discounts and combining these salient pricing strategies with nudges in a supermarket setting seems to stimulate healthy food purchases for both low and high SEP populations. However, further research in real-world settings is needed.

TRIAL REGISTRATION

This randomized trial ( NTR7293 ) was registered in the Dutch trial registry ( www.trialregister.nl ).