Never trust anyone after lunch. People tend to be a lot more scrupulous in the morning, a new study from Harvard and University of Utah researchers suggests. In a series of experiments, people were asked to solve math problems—some of which were impossible—either in the morning or afternoon, and were told they'd be paid five cents per correct answer. They were then asked to self-report their scores. The result: Afternoon people were 20% to 50% more likely to cheat, the Harvard Business Review reports.
Our self-restraint is stronger in the morning because our energy stores are higher, Scientific American explains. As our batteries drain—and this study suggests that even everyday activities drain them—we become less ethical. Another factor is sleep, which is needed to recharge our moral batteries. (Read more honesty stories.)