Pro-environmental decisions are hampered by their opportunity costs – evidence from effort-based decision-making

Pro-environmental behavior is often conceptualized as a trade-off between environmental benefits and the associated costs: a person engages in a pro-environmental behavior if the value of the environmental benefit outweighs the time, effort, or money required to generate it. However, pro-environmental behavior does not occur in a vacuum: behaving pro-environmentally most often implies not engaging in competing behaviors, but the associated opportunity costs have rarely been considered in previous work. Here, we study pro-environmental behavior as an effort-based decision-making process to better understand how pro-environmental behavior is shaped by the costs and benefits of competing behavioral options. In two studies (N = 115, N = 255), participants were asked to choose between exerting effort to obtain monetary rewards either for themselves or for the environment. By manipulating reward magnitude and effort level of each option orthogonally, we found that smaller environmental rewards led to increased effort discounting, that is, the level of effort affected decisions more at low levels of environmental reward. This effect was especially strong when the alternative (self-benefitting) option was effortful and/or carried low incentive value, suggesting that the effort related to pro-environmental behavior is most relevant at low opportunity cost.