In times of climate crisis, promoting sustainable behavior is becoming increasingly important – for example, driving less, eating less meat, or choosing reusable instead of disposable products. However, motivating people to adopt such behaviors can be challenging. The reason: unlike other goals (such as exercising to achieve better fitness), sustainable behaviors often aim to prevent a negative outcome (e.g., the intensification of climate change). As a result, the impact of individual decisions often remains invisible. For instance, when choosing between a disposable and a reusable coffee cup, it is often unclear what difference one's own actions actually make.
In three experiments, we investigated how the impact of sustainable behaviors can be made more visible in order to increase motivation. To do this, we showed participants various figures illustrating how many disposable cups could be saved by regularly using a reusable cup – for example, every workday over a period of four weeks. The savings were presented in two different ways: as a daily saving (i.e., saving one disposable cup each day) or as a cumulative saving (i.e., saving 20 disposable cups after four weeks).
The results show that a cumulative presentation is more effective: participants who saw cumulative figures perceived the use of reusable cups as more impactful and were, in turn, more motivated to use them. However, this effect only occurred when the displayed savings were perceived as sufficiently large. The benefit of the cumulative format was evident when the savings amounted to 20 disposable cups in four weeks, but not when the savings were 48 cups over the course of a year.
Our conclusion: if sustainable behavior is to be perceived as effective, it helps to present the positive effects cumulatively over time. Our findings show that such visualizations can boost motivation – provided that the overall savings are perceived as meaningful.