Think the answer may be "when his wife's out of town"? Think again. According to recent research, the answer may have far less to do with circumstance than it does with time of day.

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According to a recent study published in "Psychological Science", both men and women are less ethical in the afternoon than they are in the morning. And while the phenomenon can apply to matters of the heart, it's far from exclusive, with researchers claiming that it also applies to how men and women interact with friends, coworkers, teachers, and bosses.

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In the study, researchers from Harvard University and the University of Utah's David Eccles School of Business had study participants look at patterns of dots on a split screen. The subjects were asked which side of the screen had more dots, then given money based on their answer. The catch? Instead of being rewarded for the right answer, participants were given ten times the amount of money if they guessed the right side of the screen, regardless of whether or not the right side was the side with more dots. And while lying occurred in both groups, researchers found that instances of cheating increased in the afternoon sessions. Not only that, but subsequent online studies on the phenomenon conducted by the team found that people were more likely to say they had solved an unsolvable puzzle in the afternoon than they were in the morning, and, most worryingly, send a dishonest message to a virtual partner.

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So why are we more prone to lying as it gets later? It's because our self-control depletes throughout the day.

"We measured self-control fatigue and found it to be the underlying mechanism contributing to this phenomenon," explains Maryam Kouchaki, PhD, co-author of the study and a fellow at the Edmond J. Safra Center for Ethics at Harvard University. And that may be especially true for people who tend to have a high standard of morality. "The most honest people may be the most susceptible to the negative consequences associated with the morning morality effect," the researchers said in a statement. In other words, if you want the best shot at a real heart-to-heart, you might want to consider asking the tough questions before breakfast.

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