‘Will you buy fewer plastic bottles?’ A simple question can change our behaviour
The bottled water market has seen explosive growth – up 73% over the last decade – making it one of the fastest-growing industries globally. However, this growth comes at a significant environmental cost. Plastic waste, greenhouse gas emissions from production and distribution, and the overexploitation of water resources all contribute to an escalating ecological crisis. Reducing reliance on bottled water is, therefore, an urgent challenge.
Public awareness of this issue has grown. A 2020 study by Futerra and OnePulse found that 80% of respondents were willing to change their habits to combat climate change, and 50% specifically considered cutting back on plastic use. Despite this, little attention has been given to communication strategies designed to reduce bottled water consumption.
The power of self-prophecies
Our research suggests that asking people questions about their future behaviour – a psychological effect known as a self-prophecy – may inspire meaningful change. In a study involving 269 participants in the United States, researchers investigated whether this tactic could reduce bottled water purchases.
Self-prophecies work by prompting individuals to predict their future actions (e.g., “Will you recycle your packaging?”). This triggers cognitive dissonance: the discomfort of recognising a gap between one’s values and behaviours. People often resolve this tension by adjusting their actions to align with their beliefs.
Guilt as a motivator
Our study uncovers the emotional mechanism that links self-prophecy prompts to pro-environmental actions, with anticipated guilt serving as the key driver. American social psychologist Leon Festinger, in his seminal work A Theory of Cognitive Dissonance, describes dissonance as a state of psychological discomfort that spurs behavioural change. While Festinger does not explicitly identify the nature of this discomfort, later theorists highlighted guilt as one of the emotions that dissonance can trigger under specific circumstances.
Building on this idea, we hypothesised that people anticipate guilt when they foresee themselves failing to engage in environmentally responsible actions, particularly when such behaviours align with their normative beliefs – social or cultural expectations of what constitutes appropriate behaviour. This anticipated guilt, we argue, motivates individuals to adopt eco-friendly practices to avoid experiencing the negative emotion.
To test this theory, we conducted an experiment measuring guilt in participants exposed to an advertisement featuring a prediction question designed to discourage bottled water purchases. Those who viewed the ad experienced higher levels of anticipated guilt compared to participants in a control group who saw an ad without the prediction element. Crucially, this guilt significantly reduced their intention to buy bottled water, demonstrating how emotional anticipation can influence behaviour.
Varying effects across individuals
We investigated two key factors that influence the effectiveness of self-prophecy techniques: normative beliefs and the motivations that drive people to act.
Research has long established the power of normative beliefs in shaping behaviour. People who strongly adhere to their beliefs are not only more likely to predict that they will act in accordance with them but also more likely to follow through. Our study delved into how different types of norms – descriptive (what most people do), injunctive (what is socially expected), and personal (internal moral standards) – affect intentions.
Our findings reveal that these three types of norms significantly influence feelings of anticipated guilt. Participants generally believed that reducing plastic bottle consumption was common, socially expected and aligned with their personal convictions. The stronger these norms, the more intense the anticipated guilt when participants considered non-compliance. However, the act of posing a prediction question did not amplify the salience of these norms during decision-making. This suggests that such questions do not inherently guide participants toward behaviour aligned with their normative beliefs.
We also examined approach motivation, the drive to seek positive experiences or rewards, measured through behavioral approach system (BAS) scores. Individuals with high scores are typically goal-oriented, pursuing both tangible rewards (e.g., acquiring objects) and abstract achievements (e.g., altruism). This heightened drive helps them actively close the gap between their personal objectives and actions.
When guilt and action don’t align
Surprisingly, our study found that individuals with lower sensitivity to rewards and less drive to seek positive experiences felt greater guilt than their more motivated counterparts. Why? These individuals, while less motivated to act, became acutely aware of the gap between their behaviours and personal norms when prompted by the prediction question. This awareness, despite their inertia, triggered a stronger sense of guilt, which in turn increased their intention to reduce plastic bottle use.
On the other hand, those with higher BAS scores seemed naturally adept at aligning their actions with their norms, minimising cognitive dissonance. Their proactive approach to achieving personal goals reduced the likelihood of experiencing guilt, as they had already taken steps to bridge the gap between their intentions and behaviours.
Using self-prophecies in environmental campaigns
Our study offers promising insights for environmental awareness efforts, suggesting that prediction-based questions can effectively encourage eco-friendly behaviours. This approach, easily adaptable by government agencies and NGOs, has the potential to make sustainability messaging more impactful.
Interestingly, the study did not find a connection between normative beliefs – what people perceive as socially accepted behaviours – and the success of self-prophecy techniques. Had such a link been observed, individuals with stronger normative beliefs might have adjusted their behaviours more significantly in line with societal norms. However, existing research consistently highlights the pivotal role of personal norms – deeply held beliefs about right and wrong – in shaping intentions and ecological actions.
We therefore recommend designing campaigns that emphasise personal responsibility and the consequences of inaction. For example, messages that underscore the urgency of environmental issues and the importance of individual contributions can amplify the effectiveness of self-prophecy interventions.
While the study primarily examined behavioural intentions rather than actual behaviours, previous research supports the long-term impact of self-prediction techniques on real-world actions. For instance, interventions have been shown to improve recycling rates over four weeks and boost gym attendance for up to six months. These findings underscore the power of a simple question to engage emotional drivers and inspire lasting sustainable practices. Läs mer…