Paying People to Protect the Environment: A Meta-analysis of Financial Incentive Interventions to Promote Pro-environmental Behaviours

Behaviours that are more difficult to perform inherently have more barriers, therefore, additional motivation provided by incentives, may be needed to encourage people to overcome these barriers. Thus, incentives may have the strongest effect on behaviours perceived to be the most difficult to perform. Pro-environmental behaviour requires participation by many people to optimise its collective environmental effect. Accordingly, incentives are an attractive intervention strategy as they can be scaled to reach a large population. However, there is an absence of evidence-based guidelines that would enable interventionists and policy makers to purposefully select a financial incentive type when designing an intervention or policy.   

Results indicated that incentive interventions generally had a small-to-medium effect on pro-environmental behaviours, both while the incentive was offered and after it had been removed, inferring that financial incentives tended to lead to a persistence of pro-environmental behaviours even after the incentive had been discontinued. Additionally, the authors mention that the effectiveness of different types of financial incentives varied by the type of pro-environmental behaviour targeted. For example, while incentives were in place, cash incentives tended to be more effective at changing recycling behaviours, and non-cash incentives tended to be more effective at changing energy conservation and travel behaviours.   

Variable schedules of reinforcement also tended to elicit greater increases in behaviour compared to fixed schedules of reinforcement, as the unpredictability keeps the individual engaged and hoping for the next reward. Variable schedules of reinforcement refer to a system where rewards (reinforcements) are given at unpredictable intervals or after a variable number of actions. This contrasts with fixed schedules of reinforcement, where rewards are given at consistent intervals or after a fixed number of actions. For future work, the authors mention that incentives that use negative reinforcement (e.g., fees for not recycling) should be further explored. Finally, additional research should strive to specify the amount of an incentive that needs to be offered, as this knowledge would also help us maximise the utility of incentive interventions.