My cup of tea: Behaviour change intervention to promote use of reusable hot drink cups

Globally approximately 16 billion paper coffee cups are being thrown away every year. One solution to this problem is using a reusable hot drink cup. We developed a behaviour change intervention to increase the use of reusable hot drink cups on an Australian University campus and evaluated its effectiveness; we also investigated the psychological mechanisms through which change happens; moreover, we extended the investigation on the previously established relationship between habit strength and intolerance of uncertainty. Participants (N = 156) from a large Australian University were randomly assigned to one of four intervention conditions: 1) an intervention aimed at evoking environmental values, 2) an intention-based intervention, 3) a habit-based intervention, and 4) a control group with no direct intervention to increase use of reusable cups. At baseline, participants in the three intervention groups received a new reusable hot drink cup, and completed a pre- and six-week post-intervention questionnaire assessing habit strength, intention to use a reusable cup, biospheric values, personal involvement and personal norms towards the environment, ecological worldview, and intolerance of uncertainty. The behaviour of using a reusable cup was recorded by participants using a phone app immediately after delivery of the intervention and at six-week follow-up. There was a significant increase in the use of reusable cups in all intervention conditions immediately after the intervention and after the six-week follow-up, compared to the control condition. The key mechanisms for behaviour change were similar between the intervention conditions, with groups increasing habit strength, especially if they had difficulty tolerating uncertainty. These findings offer suggestions for establishing habits in pro-environmental behaviour change interventions, as well as for tailoring habit-based interventions for those who are intolerant of uncertainty.