Association of Self‐Reported Sleep and Circadian Variability and Moral Judgements and Decision‐Making

Sleep and social processes are bidirectionally interrelated. Circadian factors such as sleep duration, quality, and chronotype can influence social processing, including moral judgements and decision‐making. We investigated the associations of self‐reported sleep and circadian factors with measures of human moral and social judgements, including online vigilantism, aversion to causing and witnessing harm, and generosity. A total of 109 healthy adults (18–39 years) completed an observational online survey of self‐report measures of sleep and circadian factors (quality, chronotype, sleep regularity, social jetlag), as well as self‐report or behavioural measures related to moral concerns, such as willingness to engage in online vigilantism, aversion to causing and witnessing harm to others, and generosity (the Dictator Game). We found significant associations between increased online vigilantism and earlier chronotype, higher sleep regularity, and less social jetlag ( r > 0.20, all p < 0.05), and between aversion to causing and witnessing harm and sleep regularity ( r > 0.20, all p < 0.05), but not for dictator game generosity ( p > 0.06). Hierarchical regression analyses identified moderate effect sizes for sleep regularity and (to a lesser extent) social jetlag as significant contributors to vigilantism and aversion to causing and witnessing harm ( R 2 > 0.21, all p < 0.05), after controlling for sociodemographic characteristics, mental health conditions, and medication intake. A small, non‐significant effect size was identified for sleep quality and dictator game generosity ( R 2 = 0.13, p = 0.06). The findings highlight the importance of considering sleep and circadian regularity in human moral judgements and decision‐making.