Reducing single-use plastic on college campuses: Theory of planned behavior-based brief interventions

Single-use plastic has devastating impacts on the natural environment and scalable theory-based interventions are urgently needed to curb plastic consumption. The purpose of this study is to test the impact of two brief plastic reduction interventions on consumption on college campuses and whether these effects will be mediated by changes in the extended Theory of Planned Behavior (TPB) model consisting of attitudes, subjective norms, perceived behavioral control, moral norms, descriptive norms, and self-identity. 375 undergraduate students (77% female) from two colleges in the southeastern US completed baseline measures of plastic consumption beliefs and behavior in line with the extended TPB model. Participants were then randomized into one of three groups - control group (n = 152), app intervention group (who tracked plastic behavior on a mobile phone app for a week and received TPB-based daily messages via push notifications; n = 89), or pledge intervention group (who made a pledge to reduce plastic for a week and received TPB-based daily messages via email; n = 134). All participants completed the survey again after the intervention week. Results showed that the extended TPB model along with the intervention condition significantly predicted changes in plastic behavior over the week, (R2 = 0.24, p < .001). Additionally, mediation analysis revealed that the pledge group (compared to the control group) reported a significant decrease in plastic consumption over the week-long intervention, with indirect effects via changes in attitudes, perceived behavioral control, and descriptive norms. The app group (compared to the control group) decreased plastic consumption less and showed no change to the extended TPB constructs. Results suggest that plastic reduction interventions that influence the extended TPB constructs can be expected to have corresponding changes in plastic consumption behavior.