The impact of one night of sleep deprivation on moral judgments.

Recent studies have shown the existence of a relationship between sleep and moral judgment. In this study, we investigated whether one night of sleep deprivation affects the ability to judge the appropriateness of moral dilemmas. Forty-eight students had to judge 30 moral dilemmas at test, after a night of home sleep, and another 30 dilemmas at retest, following one night of continuous wakefulness. The 60 dilemmas (20 moral impersonal, 20 moral personal, and 20 non-moral) were selected from Greene's dilemmas. Both groups judged the appropriateness of personal and impersonal dilemmas in the same way. A close to significant effect of sleep deprivation was observed on the reaction times for impersonal moral dilemmas, to which the deprived subjects responded faster (p = .05) than the control subjects. However, this was not the case for personal ones, for which no difference was significant. This result shows a greater ease/speed in responding to the (impersonal) dilemmas, which induce low emotional engagement after sleep deprivation, although the willingness to accept moral violations is not affected. This suggests that one night of sleep loss selectively influences the response speed only for moral impersonal dilemmas, probably due to disinhibition processes. The quality of moral judgment dilemmas does not seem to be easily influenced by a single night of sleep deprivation, but only by a longer lack of sleep.