Why you shouldn't schedule anything important for 2 p.m.

Ben Tinker, CNN | 8/23/2017, 6:07 a.m.
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"Outside of 'time of day' variables, multiple lines of evidence suggest that neural activation is higher in rewards regions in response to unexpected rewards, compared to expected rewards," Byrne said. "A good analogy for this is your response to a surprise birthday party in comparison to a planned birthday dinner. Both are rewarding events; however, when the rewards are unexpected, your brain has to work harder to understand what is happening."

Implications for daily life

Prior research has shown that it might be harder for you to think clearly, exercise good judgment and avoid making mistakes in the afternoon. This study is provides more evidence that it's not only what you do that matters, but when you do it.

Science has shown there are many ways to optimize daily life activities around your circadian rhythm.

Psychologist Eric Barker says you should always organize your to-do list from worst to best, knocking out the things you don't want to first, since "your self-control is at its peak first thing in the morning." Save the mindless tasks for the afternoon, he says.

"Some fitness gurus recommend working out first thing in the morning, because that's when you're least likely to have scheduling conflicts and therefore more likely to exercise regularly," says Robert J. Davis, author of "Fitter Faster." But you actually perform best at exercise later in the day, he says.

Even weight loss can be tied to when, not just what, you eat. "Skipping meals or eating too few calories earlier in the day appears to stack the odds against us," says nutritionist Lisa Drayer, a CNN contributor. "More and more research points to the fact that when you front-load your calories instead, you have a much better chance of shedding pounds."

Investigating how to better treat diseases affected by the body's internal clock -- such as depression, substance abuse and sleep disorders -- is something Byrne would like to study next.

"A range of evidence suggests that circadian rhythms are less robust in people vulnerable to depression and bipolar disorders, and we have shown that depression is indeed associated with a blunted circadian reward rhythm," she said.

She thinks patients could benefit from a more precise focus on when they receive their treatment, maximizing rewarding experiences in the middle of the day and minimizing them at night.