Eight hours of uninterrupted sleep per night—it’s so widely recommended it approaches an axiom. The strange thing is, there’s nothing natural about it. In a landmark 1992 study, Thomas Wehr demonstrated that humans, like many other animals, are naturally inclined to sleep in bouts, separated by periods of activity. Given 10 hours per day of light, instead of the modern sixteen hours of artificial lights-on time, subjects sleep in two symmetrical blocks of several hours each. In the middle of the night, they wake up fully for up to three hours.
In 2010, I gave a talk at TEDGlobal in which I described this alternative sleeping pattern as a candidate for our ancestral sleep schedule. Pre-industrial literature from Canterbury Tales to Wuthering Heights describes a “first sleep” (sometimes called “beauty sleep” or “dead sleep”) and a “second sleep” in early modern English society. And ever since that talk was translated into 39 languages and approached the two-million-view mark, I have been receiving emails from polyphasic sleepers—people who sleep in spurts around the clock.
There is a seemingly inexhaustible supply of people who want to experiment with their own sleep. With the rise of productivity culture, time is money, both in the literal sense and in a broader kind of experiential currency. Many resent the third of their lives lost to unconsciousness and wish to be present for more of it. Some of those people—overwhelmingly male, in late adolescence—try sleeping polyphasically, in bits. If naps can be refreshing, the logic goes, perhaps that’s all we really need.