Sex-specific associations of estradiol and instrumental harm with moral decision-making

Previous research suggests that women and men may differ in moral decision-making involving instrumental harm. However, prior findings have yielded inconsistent explanations for these differences, suggesting effects of gender expression, empathy, action tendencies, and biological causes, such as differences in gonadal hormone levels. Yet, no data exists on the effects of endogenous estradiol and progesterone on moral decision-making, while the effects of testosterone are inconsistent. Our study aimed to close this research gap. A sample of 137 cis individuals (73 women, 64 men) completed a moral dilemma task based on the Consequences, Norms, Inaction (CNI) model either in the morning or evening. Relevant personality traits, including agreement with instrumental harm, impartial beneficence, empathy, and gender expression, were assessed via self-report. Blood samples were analyzed for estradiol, progesterone, testosterone, and cortisol. Contrary to prior literature, no behavioral differences between women and men were observed in moral decision-making. However, self-reported agreement with instrumental harm positively predicted sensitivity to consequences and negatively predicted adherence to moral norms in the whole sample. Estradiol concentration positively predicted sensitivity to consequences in the morning women group, and general inaction tendency in the morning men group. Overall, these findings highlight the joint influence of biological and personality factors on moral choices and hint towards subtle sex/gender differences.