What factors influence the choice between fish and meat among grocery shoppers? Insights from an unsuccessful nudge intervention

Food production is the human activity with the greatest impact on the earth systems and account for about a quarter of all greenhouse gas emissions. Reducing consumption of certain meat (e.g., beef, pork and lamb) and replacing it with proteins with less environmental impact has been highlighted as one of the greatest leverage points to achieve a more sustainable food system. In this study we evaluate a nudge intervention at a medium sized grocery store designed to reduce purchases of meat in favour of fish with a lower environmental impact. We also measure other relevant internal and external factors influencing this choice, such as values, attitudes, habits, demographics and price. To explore how the nudge influenced shopping decisions we designed a natural field experiment in the store and measured the effect by collecting data on sales of fish (85 215 items sold over 143 days). To further evaluate the nudge and to explore how the other factors influence the choice of protein we collected data from a selected sample of customers (N=200). The results failed to show evidence for the effectiveness of the nudge intervention, instead we found that values, habits, attitudes and price all significantly influenced this protein choice. Our results highlight the complexity of shopping decisions and how nudge interventions are not always easy to implement, adding important null-findings to the available literature. We discuss policy implications of these findings, possible improvements to the nudge and how interventions that aim to steer similar shopping decisions might need to account for habit breaking to be effective.