A new study suggests that too little sleep makes tough moral decisions that much tougher. 

"Our results simply suggest that when sleep deprived, individuals appear to be selectively slower in their deliberations about moral personal dilemmas relative to other types of dilemmas," said William D.S. Kilgore of the Walter Reed Army Institute of Research.

As part of the study, 26 healthy adults were asked to judge the appropriateness of different responses to three types of moral dilemmas.  They did this while fully rested and then did it again after they'd been awake for 53 hours.  When sleep-deprived, the study participants took much longer to respond to the moral dilemmas, suggesting that it was much more difficult for them to decide on a course of action compared to when they were fully rested.

The researchers who worked on this study emphasized that the study's findings do not support the notion that sleep deprivation actually lowers a person's moral standards.