Early risers are more likely to cheat and behave unethically in the night hours, scientists, including one of Indian-origin, have found.
Researchers have found that early-rising "larks" and late-night "owls" had different levels of honesty depending on the time of day.
The study, by Sunita Sah, research fellow at Harvard University in the US, and colleagues examined the behaviour of almost 200 people - with the subjects taking part in problem-solving tests and games without realising that it was their honesty that was being measured.
The study examined the relationship between ethical decision making and people's "chronotype" - which is when individuals are most likely to want to be asleep or when they have more energy.
It found a significant link between people being more likely to be honest when it fitted in with their chronotype, 'BBC News' reported.
This meant that the early-rising "larks" were more ethical in the morning - and the "owls" were more likely to be honest at night.
Researchers found that the level of dishonesty was found to be heightened when people were outside of their preferred time of day.
In the morning, evening people are more unethical than morning people, the study found.
The research was carried out by academics at Johns Hopkins University and the University of Washington, and Sah is an assistant professor of business ethics at Georgetown University as well as a research fellow at Harvard.
Sah said the findings have major implications for workplaces relying on ethical decisions and honesty - particularly where there are shift patterns.