According to recent research, when people's energy wanes, they are more likely to behave unethically. As a general rule, that means we behave less well in the afternoon. But not everyone's energy ebbs and flows in the same pattern. Night owls tend to reach their peak later in the day; morning people ("larks") are more alert earlier.
There's already evidence that night people and morning people work differently. People who stay up late at night, according to one study, exhibit a higher incidence of Machiavellianism, psychopathy and narcissism. Morning people get better grades (although teens who tend to stay up later score higher on general intelligence). The researchers looking at the relationship between energy and ethics—Christopher Barnes, at the University of Washington, and his colleagues—wondered: Is it possible that morning people are more likely to act unethically at night and night people in the morning?
Barnes and colleagues set out to test this hypothesis. They designed an experiment where participants were randomly assigned to an experiment—designed to test their propensity for ethical behavior—early in the morning (7-8:30am) or late at night (midnight-1:30am). Then, as the researchers described in the Harvard Business Review:
Participants undertook a die rolling task previously established as a test for unethical behavior. In this task, they anonymously rolled a die and reported the number back to us, and we paid paying them based on the number they reported (higher amounts for higher rolls).
Although we didn't know what numbers participants actually rolled, we did know that everyone should report an average of 3.5. So any systematic differences across conditions (morning people in the morning vs. evening people in the morning, for example), would indicate cheating. Consistent with our prediction, an interesting and statistically significant pattern emerged. Larks in the night session reported getting higher rolls (M=4.55) than larks in the morning sessions (M=3.86), and owls in the morning session reported higher rolls (M=4.23) than owls in the night sessions (3.80). This evidence is consistent with the idea that larks will be more unethical at night than in the morning, and that owls will be more unethical in the morning than at night.
It's probably inadvisable to take these conclusions as some sort of law, but it's another piece of evidence that morning people and night people get through days differently. It's far from the first study to suggest there are real differences, at least on average, between the extremes.