Sleeping over moral dilemmas modulates utilitarian decision-making

Moral decision-making depends on the interaction between emotional and cognitive control processes, which are also affected by sleep. Here we aimed to assess the potential role of sleep in the modulation of moral decisions over time by testing the change in behavioral responses to moral dilemmas over time (1 week). Thirty-five young adults were tested twice, with one week between the sessions. In each session, participants were presented with 24 sacrificial (12 Footbridge- and 12 Trolley-type) and 6 everyday-type moral dilemmas. In sacrificial dilemmas, participants had to choose whether or not to kill one person to save more people (utilitarian choice), to judge how morally acceptable the proposed solution was, and how they felt in terms of valence and arousal during the decision. In everyday-type dilemmas, they had to decide whether to pursuit moral violations involving dishonest behavior. Between the sessions, the participants' sleep pattern was assessed via actigraphy. We observed that participants reduced the utilitarian choices in the second session, and this effect was more pronounced for the Trolley-type dilemmas. We also showed that after a week participants judged the utilitarian choices as less morally acceptable, but there was no change in self-reported emotional reactivity (i.e., valence, and arousal). Moreover, sleep efficiency was mildly negatively associated with the changes in decision choices and moral acceptability for the Footbridge-type dilemmas. Taken together, our data suggest that dealing with a moral situation engages several interacting factors that seem to go beyond the competing roles of cognitive and emotional processes.