I'll have what She's having (but not what They're having): The moderating role of group membership in the effect of social norms on food choice in an online environment

The modern food-rich environment has contributed to the rise of unhealthy diets linked to noncommunicable diseases. Previous in-person research has found that the effect of social norms on food intake is greater when set by a perceived in-group member relative to an out-group member. Given recent increased social media use, we investigated whether this effect of group membership extends to food choices and to normative information presented remotely online. Participants (N = 179 female university students, 18-32 years) viewed a Facebook page pertaining to either their university (in-group) or a rival university (out-group). They were presented with either a healthy or an unhealthy norm via a post in which a student discussed their order at a café on the relevant campus. Food choice was assessed through an online menu where participants were asked to order one main, side, and dessert dish. As predicted, participants who viewed the healthy norm ordered a higher percentage of healthy items (especially in the desserts category) relative to those who viewed the unhealthy norm. However, this effect was significant only for those in the in-group condition; there was no such pattern for participants in the out-group condition. These findings provide insight into the role of group membership in the effect of social norms, and have practical implications regarding the design of identity-based social media health campaigns to promote healthier eating behaviours.