Social norm intervention in real-world supermarkets in the Netherlands: A quasi-experimental evaluation of effects on perceived social norms and meat substitute purchases.

Social norm perceptions are implicit rules of conduct that describe what is normal and acceptable behavior. Changing social norm perceptions through textual and physical social norm communications can be a promising approach to changing behavior. Past studies, however, primarily relied on controlled (lab) experiments, leaving it unanswered to what extent these norm communications relate to social norm perceptions in a complex context. The present study addresses this issue for meat substitute purchases: to what extent can a social norm intervention in real-world supermarkets stimulate meat substitute purchases, and to what extent do social norm perceptions favoring meat substitute purchases mediate this relationship? A 13-week social norm intervention was implemented in three experimental supermarkets (with n = 3 matched control stores). Social norms were communicated textually on stickers and banners in the meat aisle and physically through increased shelf space for meat substitutes and island shelves with legumes. A total of N = 639 participants (n = 327 control) completed a survey upon exiting the supermarket, measuring social norm perceptions and collecting receipts to measure meat substitute purchases in grams. Results show that the likelihood of meat substitute purchases was OR = 3.6 times larger in intervention supermarkets (B = 1.28, SE = 0.512, z = 2.50, p = .012) than in control stores. However, their norm perceptions did not differ between intervention and control stores. In sum, a social normative intervention in a complex surrounding may impact purchasing behavior, but the mechanism driving this remains to be identified.