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.
- Gradual acceptance of the notion that sequential sleep hours are not essential for high-level job performance has led to increased workplace tolerance for napping and other alternate daily schedules.
- Employees at Google, for instance, are offered the chance to nap at work because the company believes it may increase productivity. Thomas Balkin, the head of the department of behavioral biology at the Walter Reed Army Institute of Research, imagines a near future in which military commanders can know how much total sleep an individual soldier has had over a 24-hour time frame thanks to wristwatch-size sleep monitors. After consulting computer models that predict how decision-making abilities decline with fatigue, a soldier could then be ordered to take a nap to prepare for an approaching mission. The cognitive benefit of a nap could last anywhere from one to three hours, depending on what stage of sleep a person reaches before awakening.
- Most of us are not fortunate enough to work in office environments that permit, much less smile upon, on-the-job napping. But there are increasing suggestions that greater tolerance for altered sleep schedules might be in our collective interest. Researchers have observed, for example, that long-haul pilots who sleep during flights perform better when maneuvering aircraft through the critical stages of descent and landing.