Our bodies aren't the only things that tire out as the day wears on -- our moral compasses may take a hit, too.
People are more likely to be dishonest in the afternoons than in the mornings because of diminishing self-control throughout the day, according to new research.
"Whether you are personally trying to manage your own temptations, or you are a parent, teacher, or leader worried about the unethical behavior of others, our research suggests that it can be important to take something as seemingly mundane as the time of day into account," study researchers Maryam Kouchaki, of Harvard University, and Isaac Smith, of the University of Utah's David Eccles School of Business, said in a statement.
Published in the journal Psychological Science, researchers conducted several experiments to gauge how time of day affects self control and unethical behavior. In one of the experiments, they had study participants look at different patterns of dots on a computer screen. The participants were instructed to say which side of the computer screen had more dots shown.
But here's the twist: While a reward was given based on the participants' answers, it was not given based on the correct answers. They were given 10 times more if they said the right side of the screen had more dots than the left side, even if it wasn't true -- in other words, there was a financial incentive to cheat.
Researchers found that participants who were given this test in the morning -- between 8 a.m. and 12 p.m. -- were more likely to actually give correct answers. But participants tested between 12 and 6 p.m. were more likely to cheat for the financial incentive.
In other experiments in the study, researchers also found that this "morning effect" held true. For instance, study participants were more likely to send a dishonest message, or say that they'd solved a problem when they hadn't, in the afternoon than the morning.
"Furthermore, the effect of time of day on unethical behavior was found to be stronger for people with a lower propensity to morally disengage," they wrote in the study. In other words, this "morning effect" seemed to hold especially true for people who usually feel guilty when they act unethically. Those who have no qualms with bad behavior, on the other hand, are more likely to cheat in both morning and afternoon.
But that isn't the only way time can affect our propensity to lie. A study published last year in the same journal also showed that the amount of time we have is also a huge factor in our truthfulness. Specifically, that study showed that people under a time crunch were more likely to lie than those given more time.
"People usually know it is wrong to lie, they just need time to do the right thing," the researcher of that study, the University of Amsterdam's Shaul Shalvi, said in a statement.
People are also more likely to lie when they have to say something out loud, versus in a text message, another study showed. Researchers from the University of Michigan Institute for Social Research found that text messaging actually seems to promote candidness, as well as more precise answers.
But at the end of the day, truthfulness is what we should all be striving for -- after all, it's good for health. University of Notre Dame researchers found last year that people who make a point not to lie are more likely to have better health, fewer feelings of tension and improved relationships.