Social Norms and Pro-Environmental Choices. Evaluating Social Norm Interventions in a Field Experiment to Promote Reusable Takeaway Containers

Abstract

The rising trend in the usage of single-use food containers gained more fuel during lockdowns and shutdowns due to
pandemic restrictions. The fact that more people had food delivered or bought it at takeaways led to an increased amount of plastic waste, which is environmentally problematic. This article reports on a field study that was conducted to test whetherinjunctive norm messages printed on posters and discounts on reusable containers can increase the percent usage of reusable containers at a takeaway. To this end, two experiments with different starting conditions, one with a low (0.2 %) percentageand one with a high (10.4 %) percentage of use, were conducted in the city of Zurich. The data were subjected to ANOVA and interrupted time series analyses to measure how the interventions affect the magnitude and trend of usage. The statistical analysis revealed that both the injunctive norm messages and the discounts positively affected the usage of reusable containers, but only if there had been a low percent usage during the pre-intervention period. The social norm had a negative effect on the trend, if the initial percent usage had been high. The findings therefore indicate that the effectiveness of easily implementable measures depends on the percentage of people who already use reusable containers.