“If you can do it, why can’t I?”: The changing impact of descriptive norms for healthy eating

Two experiments assessed university students’ intentions to eat healthily as a function of measured variables (the Theory of Planned Behaviour) and manipulated injunctive and descriptive group norms. In Experiment 1, 119 students were exposed to a positive injunctive norm that “UQ students approve of eating healthily” or a negative descriptive norm that “UQ students do not eat healthily", or both, or neither norm. A significant interaction between the injunctive and descriptive norm was identified. When a negative descriptive norm was present, participants exposed to a positive injunctive norm reported significantly lower intentions to eat healthily. When no descriptive norm was given, the injunctive norm had no effect. Nevertheless, the results suggest the importance of investigating the interacting effects of referent group norms and their influence on ones behaviour. Experiment 2 investigated the potential mediators and moderators of the positive injunctive and negative descriptive interaction. One hundred and twenty three students were presented with a positive or negative injunctive norm, and a positive or negative descriptive norm regarding UQ students’ healthy eating. Unexpectedly the interaction in Experiment 1 was not replicated. However, self efficacy was found to be a moderator of conformity to descriptive norms. Participants low in self efficacy reported marginally higher intentions to eat healthily when exposed to a positive descriptive norm than a negative descriptive norm. Unexpectedly, participants high in self efficacy reported significantly lower intentions to eat healthily when exposed to a positive than negative descriptive norms. The theoretical and practical implications of Experiments 1 and 2 are discussed, as well as directions for future research