At 10:51 a.m. on a Tuesday, most working professionals — or at least the nine to fivers — are hard at work and surrounded by their colleagues. In a professional setting, we’re all expected to act professionally, but, as some bankers can attest to, once 5 p.m. hits, the cocaine parties begin. All ethical behavior is left at work. A new study is blurring the lines between ethical and unethical behavior, and has found that it may be less about who is and isn’t, and more about what time of the day it is.

We all know there are some people who are night owls and some who are morning larks, as the researchers, from Harvard University and the University of Utah, categorize them. They found that both have differing moments where unethical behavior is more likely, and that it has everything to do with when their energy is highest. For morning people, ethical behavior is more likely to take place in the mornings, when they’re better able to control their decisions. By the nighttime, they’ve spent all their energy. It’s the opposite for night people, who go about their day in a stupor, only to become energized at night, and thus, more willing to make ethical decisions.

The research builds on previous findings from Harvard, which found that people were less likely to lie, cheat, and steal before noon. With their new study, the researchers wanted to see whether the opposite occurred in people who tended to be more energized at night. “Building from this research, we predicted that larks and owls would follow different patterns of ethical and unethical behavior,” the researchers wrote in the Harvard Business Review (HBR). “Because their energy levels should follow different patterns, and this energy is crucial for resisting temptation, we expected larks to be more unethical late at night than early in the morning, and owls to be more unethical early in the morning than late at night.”

So, with two different experiments, they tested the trustworthiness of two groups of people. For their first experiment, they gave participants a simple matrix test — probably along the lines of these. Each participant was given a financial incentive to solve the problems correctly, with each solved problem earning them money. They also had the freedom to tell the researchers either the truth about how many they solved, or a lie, under the assumption that the researchers weren’t going back to check. As they had hypothesized, larks were indeed more honest in the morning while owls were more honest at night.

Their second study also relied on the veracity of self-reported results. This time, a new group of participants were given a die, and told to report the number they rolled during two sessions, from 7 a.m. to 8:30 a.m. and 12 a.m. to 1:30 a.m. Higher numbers earned more money, but the researchers knew that each person would report an average of 3.5. Once again, their hypothesis was followed through. Morning people reported an average of 4.55 at night while reporting an average of 3.86 in the morning. Conversely, night people reported an average of 4.23 in the morning and 3.8 at night.

The research offers useful information for employers and managers who might be interested in maximizing their benefit when it comes to structuring their employees’ work, the researchers said. “Managers who ask a lark to make ethics-testing decisions at night, or an owl to make such decisions in the morning, run the risk of encouraging rather than discouraging unethical behavior,” they wrote for HBR. People who are self-employed may also benefit from structuring their work at times that they have the most energy, obviously, as it will help them make the best decision for everyone involved.

The research will be published later this year in the journal Psychological Science.