Choosing others or the environment? Neurocognitive evidence for moral conflict and priority of prosocial over pro-environmental values

Should one take a flight to support refugees after a natural disaster or avoid the trip to reduce one’s carbon footprint? Using electroencephalography, the present study investigated the decision-making processes engaged when individuals are forced to choose between social and environmental behaviors based on their moral content. In this pre-registered study, a total of 127 young adults (19–30 years old) completed a two-alternative forced-choice moral decision task based on a newly developed stimulus database contrasting pro-social, anti-social, pro-environmental, and anti-environmental behaviors. Behavioral measures (decision times modeled with ex-Gaussian distributions, perceived difficulty), drift diffusion modeling, and neural activity (FMθ) were combined to estimate moral conflict during such decisions.Results showed that (1) participants readily discriminated between moral and immoral behaviors, whether social or environmental, although the underlying decision processes were not fully identical; (2) choices opposing social and environmental options elicited a pronounced moral conflict, reflected in longer and more variable decision times, higher evidence accumulation requirements, prolonged non-decision processes (e.g., mnemonic or premotor components), reduced FMθ activity as a marker of response inhibition, and greater subjective difficulty; (3) participants ultimately favored social over environmental behaviors, consistent with the existence of a pre-existing moral hierarchy; and (4) when environmental options were chosen, this decision was associated with an additional cognitive cost, particularly when immoral behaviors were involved. These findings are in line with dual-process theories, suggesting that intuitive, emotion-based processes may preferentially support pro-social decisions, whereas pro-environmental choices rely more strongly on deliberative and analytical processes. Finally, our results point to inter-individual differences in moral priorities toward the environment, which warrant further investigation.