Lack of sleep can affect people’s moral judgement, a new study shows. The findings could have implications for people in positions of responsibility, whose decisions often have life or death consequences, such as overworked medical professionals and sleep-deprived soldiers.

William Killgore and colleagues at the Walter Reed Army Institute of Research in Silver Spring, Maryland, US, set up an experiment with 26 healthy adults, all of whom were active-duty military personnel.

The participants were presented with a variety of hypothetical dilemmas, first when well rested and later, after staying awake for 53 hours. Situations included complex moral quandaries such as having to choosing whether or not to let one person die in order to save the lives of several others. Less weighty dilemmas without a moral component were also included, such as “is it OK to substitute ingredients in a chocolate brownies recipe?”

While participants did not become less “moral” when sleep deprived, they did require two seconds longer on average to answer complex moral questions, Killgore says. However, questions without a moral component did not take longer to answer after participants were kept awake.


Asleep at the wheel

The findings, along with previous brain-imaging studies, suggest that sleep deprivation has a particularly debilitating effect on decision-making processes that depend heavily on emotion. “When people go for more than 24 hours without sleep there are dramatic decreases in brain activity in the prefrontal cortex [the area of the brain involved in processing emotions and decision-making],” says Killgore. “It basically goes to sleep.”

Sleep deprived participants also showed slight shifts in what they deemed appropriate actions compared to when they were well-rested. The changes were more pronounced in individuals who scored lower in “emotional intelligence” tests. Killgore believes that those with a lower emotional capacity to begin with may have less resistance to the affects of sleep deprivation.

Judy Illes at the Center for Biomedical Ethics at Stanford University, California, US, says the study’s implications are profound. “Moral judgements are perhaps the most complex decisions that people have to make, decisions that are laden with personal, social, religious, and cultural values,” she says.

“We don’t want tired irritable soldiers making bad decisions that endanger themselves or others that are not a threat to them. Nor do we want health care providers who are unable to make quick medical decisions on behalf of their patients.”

Both Illes and Killgore are quick to note that further research, including brain imaging, should be conducted as laboratory results do not always translate to real world situations.

Journal reference: Sleep (v 30, p345)