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 an experimental paradigm designed to quantify how people discount effort (measured via a grip-force device) and time (operationalised as waiting time) for self-benefitting 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 a 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. Finally, when linking experimental behaviour to self-report measures, we found that participants who were more motivated to invest time and effort for the environment also reported greater willingness to support costly climate change mitigation policies, whereas climate change beliefs were not significantly associated with the cost-incurring task behaviour. Our approach highlights differences in how individuals respond to costs associated with personal vs environmental benefits and presents a promising tool for further research on environmental decision-making.