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A shift from predominantly animal-based to plant-based consumption can benefit both planetary and public health. Nudging may help to promote such a shift. This study investigated nudge effects on plant-based alternatives to meat and dairy in an online supermarket. We conducted a two-arm, parallel-group, randomized controlled real-life online supermarket trial. Each customer transaction was randomized to a control arm (regular online supermarket) or an intervention arm (addition of placement, hedonic property and dynamic social norm nudges promoting meat and dairy alternatives). Outcomes were the aggregate of meat and dairy alternative purchases (primary outcome), the number of meat purchases, dairy purchases, meat alternative purchases, and dairy alternative purchases (secondary), and retailer revenue (tertiary). Generalized linear mixed models with a Conway-Maxwell Poisson distribution were used to estimate incidence rate ratios (IRRs). Analyzed data included 8488 transactions by participants (n = 4,266 control arm, n = 4,222 intervention arm), out of which 2,411 (66%) were aged above 45 years, 5,660 (67%) were females, and 1,970 (23%) lived in socially disadvantaged neighborhoods. Intervention arm participants purchased 10% (IRR 1.10 (95% CI 0.99-1.23)) more meat and dairy alternatives and 16% (1.16 (0.99-1.36)) more meat alternatives than control arm participants, although these findings are not statistically significant. There was no difference in dairy alternative purchases (1.00 (0.90-1.10)). Intervention arm participants purchased 3% less meats (0.97 (0.93-1.02)) and 2% less dairy products (0.98 (0.95-1.02)) than control participants. Retailer revenue was not affected (0.98 (0.95-1.01)). Online nudging strategies alone did not lead to a statistically significant higher amount of plant-based purchases, but replication of this work is needed with increased study power. Future studies should also consider nudging strategies as part of a broader set of policies to promote plant-based purchases. TRIAL REGISTRATION: Prospectively registered on 14 th of May 2022. ISRCTN16569242 (https://doi.org/10.1186/ISRCTN16569242)., Competing Interests: Declaration of competing interest All authors declare that they have no conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Social norm perceptions are implicit standards describing what is typically done or seen as acceptable and have shown to be important both in sustaining meat consumption as well as facilitating meat reduction. Norm perceptions depend on individual differences and the contexts (e.g., supermarket, restaurant). Yet, evidence how norm perceptions differ within and across individuals is scarce. The primary aim of this study was to investigate how descriptive, injunctive, and personal norms perceptions favouring meat consumption differ across contexts and meat consumer groups. The second aim was to investigate how generic dynamic norm perceptions vary across meat consumer groups. British meat eaters (n = 1205, 25-65 years) participated in an online cross-sectional survey. Weekly meat, fish and meat substitute consumption was measured with the adapted Oxford Meat Frequency Questionnaire. All but dynamic norm perceptions were measured for the supermarket, restaurant and worksite cafeteria context. Dynamic norms were measured without a specified context. A two-step cluster analysis was conducted to identify meat consumer groups. Descriptive norm perceptions favouring meat consumption were strongest in supermarket and restaurant contexts, compared to the worksite cafeteria. Injunctive and personal norms favouring meat consumption were both perceived strongest in the supermarket, followed by the restaurant, and least in the worksite cafeteria context. Four meat consumer groups were identified and those with higher meat intake (i.e., Meat lovers and Exceeders) perceived norms favouring meat consumption stronger and norms favouring meat avoidance weaker than the groups with lower meat intake (i.e., Flexitarians and Moderates). While norm perceptions differed between meat consumer groups, the pattern of contextual differences is similar for these meat consumer groups. Our findings underscore the importance of considering contexts and meat consumer groups in efforts to reduce meat consumption., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The interplay of influences shaping dietary behaviors of adolescents needs to be well-understood to develop effective strategies stimulating healthy and sustainable behaviors. This study aimed to identify the most relevant, urgent, changeable and effective motivators and barriers of healthy and sustainable dietary behaviors among adolescents (10-19 years), as perceived by an inter- and transdisciplinary expert panel. Experts working in practice (N = 19) and academia (N = 13) - in the field of sustainability, health, nutrition and/or education - participated in this exploratory mixed-methods study. Five online semi-structured focus groups were conducted (6-7 participants). Data was thematically analyzed by two coders independently, using the socioecological framework. Subsequently, the same experts individually selected the five most relevant determinants and rated those on their urgency, changeability and effectiveness through an online questionnaire (N = 21). Participants revealed a wide system of 31 main determinants including 173 sub-determinants that motivate or hinder healthy and sustainable eating among adolescents. This system of determinants was mapped on the different layers of the socioecological model: individual factors (25 motivators; 30 barriers), social environments (15 motivators; 13 barriers), physical environments (18 motivators; 15 barriers), macro-level environments (19 motivators; 38 barriers). 'Role of peers' (social environment) was selected most as a determinant to be targeted in interventions (N = 13; urgency (M = 6.38) changeability (M = 3.85), effectiveness (M = 5.62)), followed by 'food environment around school' (N = 9; urgency (M = 5.78) changeability (M = 3.44), effectiveness (M = 5.44)), 'social influences' (N = 7; urgency (M = 5.43) changeability (M = 4.00), effectiveness (M = 5.71)), 'autonomy in development' (N = 7; urgency (M = 6.00) changeability (M = 4.29), effectiveness (M = 5.86)) and 'food availability' (N = 7; urgency (M = 6.29) changeability (M = 3.29), effectiveness (M = 6.29)). The prioritized determinants indicate that adolescents should be provided more supportive social and physical environments that promote healthy and sustainable dietary behaviors, taking into account their growing autonomy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Introduction: Adherence to behavioral measures such as physical distancing are key to mitigating the effects of viral pandemics such as the COVID-19 pandemic. Adherence depends in part on people's perception of what others do (descriptive norms) or approve of (injunctive norms). This study examines the effects that exposure to images depicting people following or breaking physical distancing rules have on perceptions of descriptive and injunctive norms and subsequent adherence behavior., Methods: An online between-subjects experiment (n = 315) was conducted, in which participants were exposed to a set of five photographs of different public spaces in which people either did or did not adhere to physical distancing rules (pre-registration: https://www.osf.io/uek2p). Participants' adherence behavior was measured using a triangulation of measures (incentivized online behavioral task, vignettes, intention measure). Perceptions of relevant social norms were also measured., Results: Mann-Whitney tests showed no effects of condition on perceptions of descriptive and injunctive norms or on adherence behavior. Linear regressions showed that both component paths of the indirect effect (condition on norm perceptions, and norm perceptions on adherence behavior) were non-significant, hence mediation analyses were not conducted., Conclusions: Exposure to images of people following (compared to breaking) physical distancing rules did not affect adherence to such rules or perceived norms. We surmise that a single exposure to such images, especially in the context of COVID-19, is insufficient to affect behavior. We therefore recommend performing a comparable experiment in which participants are exposed repeatedly to images showing people (non)adhering to a specific behavior in a particular context for a longer period., Competing Interests: The authors have declared that no competing interests exist.

It is widely accepted that physical food environments can contribute to unhealthy eating, but less is known about how physical cues in these environments actually stimulate eating. Our study starts from the assumption that social norms are embedded in physical cues and aims to make an inventory of physical cues that communicate what is socially accepted as normal and/or appropriate to eat in a Dutch outside-the-home food context. In Study 1, we conducted a qualitative study in which photographs taken in self-service food environments were analyzed using strategies from photo documentation and semiology. Grounded theory was applied to identify a wide variety of specific physical cues that were ultimately grouped into 18 higher level categories of physical cues (e.g. consumption traces, product availability). Most cue categories were associated with either descriptive or injunctive social norms, but some were associated with both types. In Study 2, we aimed to quantitatively cross-validate the social norm interpretations among laypeople (N = 173) by focusing on two selected photographs. More than half of the physical cues that participants identified in these photographs as being influential had been identified in Study 1 as cues bearing a normative message. The results further indicated that other people's behavior is easier to recognize in physical food environments than signals about what ought to be done. Given the great variety of identified physical cues associated with social norms, we posit that social norms are widely embedded in food environments and might guide eating behavior. Further research should study the effects of these cues on behavior and test whether the underlying process can be attributed to social norm interpretations., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Portion sizes of commercially available foods have increased, and there is evidence that exposure to portion sizes recalibrates what is perceived as 'normal' and subsequently, how much food is selected and consumed. The present study aims to explore the role of social (descriptive and injunctive) and personal portion size norms in this effect. Across two experiments, participants were either visually exposed to (Study 1, N = 329) or actually served (Study 2, N = 132) a smaller or larger than normal food portion. After 24 h, participants reported their intended consumption (Study 1) or served themselves and consumed (Study 2) a portion of that food and reported perceived portion size norms. In Study 1, visual exposure to portion size did not significantly affect intended consumption and perceived portion size norms. In Study 2, participants consumed a smaller portion of food when they were served a smaller rather than a larger portion the previous day, which was mediated by perceived descriptive and injunctive social (but not personal) portion size norms. Results suggest that being served (but not mere visual exposure to) smaller (relative to larger) portions changes perceived social norms about portion size and this may reduce future consumption of that food., Competing Interests: The authors declare no conflict of interest. E.R. has received research funding from Unilever and the American Beverage Association, but does not consider this to be a conflict of interest for the present research. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Purpose: The purpose of this paper is to test whether the IKEA-effect (Norton et al. , 2012) - better liking for self-crafted products than for identical products crafted by others - can be exploited to increase liking and consumption of vegetable snacks in children., Design/methodology/approach: A between-subjects experiment was conducted at an after school care facility. In total, 86 children aged four to six either crafted a peacock with vegetables or with non-food objects following an example. After the task, children ate snack vegetables ad libitum, and rated their liking for the vegetables and pride in crafting the peacock., Findings: No significant main effect of the vegetable snack creation on consumption and liking was observed. Also, perceived pride did not mediate the effect of self-crafting vegetable snacks on consumption of and liking for vegetables., Research Limitations/implications: Vegetable consumption did not differ between children who were either simply exposed to vegetable snacks while crafting or those who were crafting the vegetable snacks themselves. The equal consumption might suggest that this is caused by simple exposure, but more research is needed comparing self-crafting and exposure to a condition where there is no initial exposure to vegetables., Originality/value: Although the IKEA-effect has been demonstrated in adults, this is one of the first studies evaluating the IKEA-effect in children and as a means to increase liking for a generally disliked product in this target group, i.e. vegetables. The IKEA-effect could not be replicated under these more stringent conditions, where the experimental set-up enabled disentangling exposure and crafting effects.