Nudging Sustainable Grocery Consumption Online by Digital Carbon Labels and Descriptive Social Norms

Background: Carbon labels and descriptive social norms have been used as ‘nudges’ to increase sustainable consumption in shopping and food environments. Aims: This experiment investigates the relative and combined efficacies of digital carbon labels and descriptive social norms to increase sustainable consumption in an online grocery shop simulation, and explores how receptive participants are to this. Method: Five hundred and forty-seven participants made product selections from ten common grocery product categories presented to them digitally. One group was presented products with carbon labels, another was presented products with a descriptive social norm, a third was presented products with both carbon labels and a descriptive social norm, while controls were presented with products only. Participants indicated how comfortable the nudges made them feel, and how far the nudges impacted their decision-making and made them more considerate of the environment. Results: Participants exposed to the carbon label and combined carbon label with descriptive social norm were significantly more likely to choose lower-emission options than controls, but there was no significant difference in product selection between controls and the descriptive social norm-only condition. Participants in nudge conditions reported feeling comfortable with both carbon labels and descriptive social norms, but rated the carbon label as having a significantly greater impact on their decision-making and in making them more considerate of the environment. Participants’ open-ended comments noted carbon labels as desirable, and offered recommendations for future research and nudge designs. Conclusion: This experiment found that while a simple, digital carbon label can significantly increase sustainable consumption online, this was not the case for the descriptive social norm in the form used by this study.