Smithsonian.com

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Famously weird people have always had weird habits. Mathematician Abraham de Moivre slept twenty hours a day and still managed to come up with all sorts of important mathematical insights. Thomas Edison and Nikola Tesla both reportedly hardly slept at all. Jay Leno sleeps four hours a night. Leonardo da Vinci slept for fifteen minutes every four hours. And Salvador Dali, perhaps the king of weird, had his own strange sleep method. New Scientist writes:

He would sit with a key in one hand, poised above a metal plate placed on the floor, and let sleep take him. As soon as he began to slumber in earnest, the key would slip from his fingers and clang against the plate – waking him immediately.

Dali felt as though sleep was a waste of time. (So did Edison, and many other influential people.) But science suggests that sleep is pretty important, which is good for those of us who like our eight hours. And studies suggest that most of us do need sleep. Perhaps those famous people are the lucky few whose genetics make them better at functioning without sleep. Live Science says that some people simply need less:

Compared with the normal mice, those with one mutant gene slept about 1.2 hours less, and mice with two mutant genes slept 2.5 hours less. The mutant mice also bounced back faster than the normal mice from sleep deprivation.

Some of us might try to fool ourselves into thinking that we’re one of these super-wakers. But we’re not, says the New York Times:

Still, while it’s tempting to believe we can train ourselves to be among the five-hour group — we can’t, Dinges says — or that we are naturally those five-hour sleepers, consider a key finding from Van Dongen and Dinges’s study: after just a few days, the four- and six-hour group reported that, yes, they were slightly sleepy. But they insisted they had adjusted to their new state. Even 14 days into the study, they said sleepiness was not affecting them. In fact, their performance had tanked. In other words, the sleep-deprived among us are lousy judges of our own sleep needs. We are not nearly as sharp as we think we are.

And this idea of an eight-hour sleep cycle is pretty new, says the New York Times:

The idea that we should sleep in eight-hour chunks is relatively recent. The world’s population sleeps in various and surprising ways. Millions of Chinese workers continue to put their heads on their desks for a nap of an hour or so after lunch, for example, and daytime napping is common from India to Spain.

Historically, people were more likely to fall asleep, wake up, and then fall asleep again. The Times again:

One of the first signs that the emphasis on a straight eight-hour sleep had outlived its usefulness arose in the early 1990s, thanks to a history professor at Virginia Tech named A. Roger Ekirch, who spent hours investigating the history of the night and began to notice strange references to sleep. A character in the “Canterbury Tales,” for instance, decides to go back to bed after her “firste sleep.” A doctor in England wrote that the time between the “first sleep” and the “second sleep” was the best time for study and reflection. And one 16th-century French physician concluded that laborers were able to conceive more children because they waited until after their “first sleep” to make love. Professor Ekirch soon learned that he wasn’t the only one who was on to the historical existence of alternate sleep cycles. In a fluke of history, Thomas A. Wehr, a psychiatrist then working at the National Institute of Mental Health in Bethesda, Md., was conducting an experiment in which subjects were deprived of artificial light. Without the illumination and distraction from light bulbs, televisions or computers, the subjects slept through the night, at least at first. But, after a while, Dr. Wehr noticed that subjects began to wake up a little after midnight, lie awake for a couple of hours, and then drift back to sleep again, in the same pattern of segmented sleep that Professor Ekirch saw referenced in historical records and early works of literature.

Older people also seem to need less sleep that the rest of us, and feeling sleepy during the day isn’t normal, Live Science says:

“Our findings reaffirm the theory that it is not normal for older people to be sleepy during the daytime,” Dijk said. “Whether you are young or old, if you are sleepy during the day you either don’t get enough sleep or you may suffer from a sleep disorder.”

But no one recommends Dali’s key method.

More from Smithsonian.com:

Better Sleep in the Golden Years?
Experiments Show We Really Can Learn While We Sleep
Go to Sleep, All-Nighter Cram Fests Don’t Work