Tiredness can more us more likely to cheat or be dishonest, researchers examining the factors behind morals and ethical behaviour have said.
In a study conducted by two academics from Harvard University and the University of Utah, researchers found people were more likely to have higher levels of self control and be more morally aware in the morning.
In the afternoon, however, even people with a seemingly strong moral compass were more likely to exhibit dishonest behaviour.
Isaac Smith, of Utah and Maryam Kouchaki, of Harvard explained: “As ethics researchers, we had been running experiments examining various unethical behaviors, such as lying, stealing, and cheating.
“We noticed that experiments conducted in the morning seemed to systematically result in lower instances of unethical behavior.”
In two experiments, participants were shown various dot patterns left on a computer. For each pattern, they were asked to identify whether more dots were displayed on the left or right side of the screen.
Instead of being given money for getting the right answers, they were rewarded based on which side of the screen they determined had more dots; they were paid 10 times the amount for selecting the right over the left.
Participants therefore had a financial incentive to cheat and select from the right.
Those tested between 8am and 12pm were less likely to cheat than those tested between 12pm and 6pm, which researchers named the "morning morality effect".
In the second part of the study, the team examined participants’ moral awareness in both the morning and afternoon. After presenting them with word fragments such as '_ _RAL and 'E_ _ _ C_ _ the morning participants were more likely to form the words 'moral' and 'ethical'.
In contrast, the afternoon participants tended to form the words 'coral' and 'effects,' which researchers argue provides more evidence for their morning morality theory.
They found even people who were less likely to morally disengage in every day life were more susceptible to cheating in the afternoon.
“Unfortunately, the most honest people, such as those less likely to morally disengage, may be the most susceptible to the negative consequences associated with the morning morality effect,” the researchers concluded. “Our findings suggest that mere time of day can lead to a systematic failure of good people to act morally.”
Results of the study are being published in the journal Psychological Science.