Pharmacologically induced stress affects moral decision certainty but not choice in military personnel

Abstract Throughout their careers, military personnel must make decisions during stressful situations with potential far-reaching moral consequences. It is currently unclear exactly how key components of the acute stress response affect moral decision-making. To this end, Dutch military personnel were recruited and exposed to pharmacological stress, in which noradrenaline was increased through administration of yohimbine and cortisol through hydrocortisone. Moral decision-making was tested using fictional war scenarios, in which deontological and utilitarian tendencies, or a compromise between the two, were assessed in a computer task. Simultaneously, markers of stress and subjective experience were measured. Stress response was confirmed, as salivary alpha-amylase, heart rate and pupil size were amplified under yohimbine, while salivary cortisol was elevated under hydrocortisone. We observed that stress did not affect moral choice tendencies, as the number of deontological, compromise, and utilitarian choices remained comparable. Similarly, other indices of morality and decision consistency were not affected by pharmacological stress. Interestingly, utilitarian decision certainty remained stable under noradrenaline, while other conditions showed utilitarian uncertainty. Moreover, cortisol increased decision certainty and decreased reaction time when more choice options were presented. Further research is needed to investigate the effects of acute stress on moral decision certainty.