Effort and time costs influence motivational asymmetries in self-benefitting vs pro-environmental decisions

Mitigating climate change requires individuals to adopt more pro-environmental behaviours, many of which come at a personal cost. Costs such as the time and effort associated with certain behaviours are integral to everyday decision-making and can significantly shape people's motivation to act. In this preregistered study, we employed a novel experimental paradigm to quantify how people discount effort (measured via a grip-force device) and time (operationalised as waiting time) for self-benefiting and pro-environmental outcomes. Participants (n = 74) could earn monetary rewards for themselves (in half of the trials) and for reducing carbon emissions (in the other half). We observed higher willingness to incur time and effort costs for self-benefitting than for pro-environmental outcomes, in particular when the rewards offered were higher. Moreover, computational modelling revealed rewards were discounted nonlinearly by both time and effort: effort discounting was best described by a parabolic function, and temporal discounting by a hyperbolic function. While climate change beliefs did not significantly predict the motivation to invest time and effort into benefiting the environment, participants who were more motivated to invest time and effort for the environment also showed a greater willingness to support costly climate change mitigation policies. Our novel approach highlights differences in how individuals respond to costs associated with personal versus environmental benefits and presents a promising new tool for future research on environmental decision-making.