Coffee or a Nap?

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Some of her most striking research looks at napping compared to drinking caffeine. In one study, Mednick had one group of subjects nap for 90 minutes, while another drank 200 mg of caffeine. She also set up a control group, who took a placebo. Then she tested her subjects on several tasks, including typing and spatial skills, such as remembering the layout of a room or a map. On both tasks, coffee drinkers performed much worse than the placebo group, Mednick said. “Of course, this is a bummer for Starbucks,” she added.

Mednick started looking into napping when she was a self-described sleep-deprived graduate student at Harvard. She was inspired by stories of great, smart nappers, such as Bill Clinton and Leonardo da Vinci. At the time, there wasn’t much research about the cognitive benefits of napping. So Mednick set out to test subjects’ cognitive abilities with and without a nap. She found that her subjects’ performance increased if they napped and decreased if they didn’t.

Finally, one day, she decided to take her own advice. She went into a colleague’s office and took a nap on his couch. She woke up an hour later, feeling wonderful. Soon, her entire lab started using the couch, much to her colleague’s annoyance. It was finally moved to a windowless room and members of Mednick’s lab started napping in shifts, including pregnant women, a young father and a night owl who liked to work late into the night. “Everyone knew about the results and felt well defended that they needed to nap,” the researcher said.

That’s not to say that all naps are created equal. It all depends on which stages of sleep you’re going through, Mednick explained. The three most important stages are Stage 1, known as rapid-eye movement, or REM, and Stages 3 and 4, known as slow-wave sleep, when the brain is moving at a slower pace. Mednick and her colleagues set out to study how the different stages of sleep impacted subjects’ performance on tests after a nap. When they only got slow-wave sleep, their performance remained stable. But when their naps included REM and slow-wave sleep, it improved. A nap that includes equal parts of slow-wave sleep and REM sleep is the perfect nap, she added.

“The more you nap and the better you sleep, the better you do,” Mednick said.