Social norms: can we use them to promote healthy eating?

Abstract

Background: Social norms can be divided into descriptive norms (i.e., how other people behave) and injunctive norms (i.e., what other people approve of). This study examined if fruit consumption in students can be increased by exposing them to any or both types of norms that promote fruit intake. Furthermore, it was hypothesized that the effect of norm exposure would be moderated by gender, need to belong, and impulsivity. Methods: A between-subjects experiment was conducted in which students were randomly exposed to a descriptive norm (n=59), injunctive norm (n=71), combination of both norms (n=65), or no norm (n=70). Need to belong was assessed with the Need to Belong Scale, and impulsivity with the Barratt Impulsiveness Scale. As outcome measure, participants had to choose between fruit or an unhealthy snack as reward for participation. Additionally, participants were invited to complete a fruit diary for three consecutive days (n=88). Logistic regression analysis was used to test for an effect on students’ choice for reward (fruit vs. unhealthy snack), and analysis of covariance to test for an effect on subsequent fruit consumption. Findings: The data showed no main effects of norm exposure, nor were the hypothesized interactions significant (p’s > .297). Discussion: The use of social norms has been advertised as a powerful tool to use in behaviour change interventions. This study shows that its power may be reduced under circumstances with minimal self-presentation concerns. Future research should further address the necessary ingredients for effective social norm interventions.