Headline: Plastic-Free July: An Experimental Study of Limiting and Promoting Factors in Encouraging a Reduction of Single-Use Plastic Consumption

To tackle the plastic problem, the worldwide campaign ‘Plastic Free July’ aims at encouraging people to reduce single-use plastics during the month of July. To get people started with new behavior patterns, so-called ‘windows of opportunity’—periods where people become open for new experiences—are expected to matter. Therefore, the current study evaluated if an arbitrary month that is framed as an opportunity for change can interrupt people in their daily routines and reduce plastic consumption. An online survey (n = 509) with repeated measures (n = 366) was conducted including one experimental and one control group. The experimental group was invited to reduce their single-use plastic consumption during July in line with the ‘Plastic Free July’ campaign. Results revealed that, in this action period, single-use plastic consumption was slightly but significantly lower in the experimental than in the control group, which did not receive any information about ‘Plastic Free July’. The campaign seemed to be more effective for participants with low pro-environmental identity. Path analysis revealed that plastic consumption (prior to the intervention) was significantly predicted by perceived difficulty, habits, and pro-environmental identity. Policy support was predicted by problem awareness, pro-environmental identity and perceived barriers. We conclude with recommendations for plastic-free purchase and policy support.