Killing for the greater good: Action aversion and the emotional inhibition of harm in moral dilemmas

Moral judgment is influenced by both automatic and deliberative processing systems, and moral conflict arises when these systems produce competing intuitions. We investigated the role of emotional arousal in inhibiting harmful action in a behavioral study of utilitarian tradeoffs in a 3D digital simulation of two classic “trolley” scenarios in which participants decided whether to harm one person in order to avert harm to five others. Physiological arousal was measured via skin conductance response in real time. Results showed that physiological arousal is increased in situations in which using personal harm is necessary to achieve a utilitarian outcome relative to when the same outcome can be achieved with impersonal harm, and is linked to a decreased likelihood of engaging in harmful action, though a test of mediation was not statistically significant. In addition, when the use of personal harm was required to save lives, arousal was higher pre-action relative to post-action. Overall, our findings suggest that physiological arousal may be part of an affective system that functions to inhibit harmful action against others.