Description
Introduction
Collective action problems, or social dilemmas, are situations where short-term individual interest conflicts with long-term collective interest, posing barriers to cooperation towards a common good. While group cooperation in collective action problems has been extensively studied as an outcome, less is known about the effects of revealing a collective action problem as a communication intervention (exposure). This study aimed to examine the effect of framing the climate impact of diets as a collective action problem on the climate footprint of food choices, compared or in combination with other behavioral interventions.
Methodology
A randomized online experiment was conducted to compare the effects of exposure to information, a collective action problem framing, or a menu nudge on the climate footprint of food choices among university students in Switzerland. Inclusion criteria were being 18 years or older, enrolled as a student at a Swiss university, and not following a medically prescribed diet. The study primarily targeted meat eaters, who self-identified as flexitarian or omnivorous.
In a 2X2X2 between-subjects factorial design, participants were randomly assigned to one of eight experimental groups, including a control condition. The primary outcome was the mean climate footprint of food choices, expressed in kilograms of CO2-equivalents (kg CO2-eq), based on a meal selection task within a university canteen scenario. Meals were designed to have varying climate footprints while maintaining nutritional quality in adherence to the Swiss dietary guidelines. The climate footprint of each meal quantified as global warming potential, was calculated using a life cycle analysis (LCA).
Results and Discussion
The study involved 2281 valid observations from three participating universities in the three major linguistic regions in Switzerland (Italian, French, and German-speaking), including 1691 meat eaters. The mean age of participants was 24.85 years old, and 63.26% (n=1443) were female. Across seven intervention groups, all interventions resulted in significantly lower food climate footprints compared to the control among meat eaters. The control group showed the highest footprint (mean 5.94, SD 2.76), while the collective action problem framing plus menu nudge showed the lowest (mean 4.74, SD 2.09). This 1.21 kg CO2 eq/week (20.37%) difference was statistically significant (t(443) = -1.21, p < 0.001, 95% CI [-0.75,-1.67]). While females had an average footprint (mean 4.69 SD 2.06), lower than males' (mean 6.16 SD 2.79), the interventions had a higher mitigation potential among male participants. Compared to the control (mean 7.36, SD 2.92), the social dilemma plus a nudge combination held most effective (mean 5.12, SD 2.19), resulting in a climate footprint 30% lower among males (t(182) = -2.24, p < 0.001, 95% CI [-1.49, -2.99]).
Conclusions
A collective action problem framing plus a nudge resulted in a 20% lower climate footprint of food choices in a student population, and 30% lower among male participants. The findings offer supportive evidence that communicating a social dilemma may foster climate-friendly choices in this high-income country setting. Further research is needed in field settings or to address other collective action problems, such as antimicrobial resistance or vaccine hesitancy.
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