“The difference between us is very marked,” wrote Frederick Douglass to Harriet Tubman in 1868. “Most that I have done and suffered in the service of our cause has been in public, and I have received much encouragement at every step of the way. You, on the other hand, have labored in a private way. I have wrought in the day—you in the night.”

In Japanese tradition, ghosts and spirits are more likely to appear at dusk or dawn than in the middle of the night. “In order for people to see them and be frightened by them,” wrote folklorist Kunio Yanagita, “emerging in the pitch-dark after even the plants have fallen asleep is, to say the least, just not good business practice.”

Into the early modern period, the word bug referred to a phantom in the dark; a 1535 translation of the Bible made for Henry VIII came to be known as the Bug Bible for its rendering of Psalm 91:5 as “Thou shalt not nede to be afrayed of eny bugges by night.” The word was changed to terrors in later editions, but the original sense still colors the common bedtime warning against letting bedbugs bite.

A longtime practice of European peasants was to bring cows and sheep inside for the night. If one could ignore “the nastiness of their excrements,” a late seventeenth-century visitor to Ireland opined, “the sweetness of their breath” and “the pleasing noise they made in ruminating or chewing the cud” might lull a person to sleep. A visitor to the Hebrides noted, however, that while urine was regularly collected and discarded, the dung was removed only once a year.

Setting grim tales during nighttime was critiqued as a cliché in 1594 by Thomas Nashe. “When any poet would describe a horrible tragical accident,” he wrote, “to add the more probability and credence unto it, he dismally begins to tell how it was dark night when it was done.”

The practice of yobai, “night crawling,” was common in rural communities in medieval Japan, and continued into the twentieth century. A young man would visit a young woman’s house after dark, disguising his features with a cloth to avoid embarrassment should his advances be rejected. These premarital liaisons could become formal if a child were conceived.

In August 2018 data scientist David Bamman examined how authors recently interviewed in the New York Times’ By the Book column answered the question “What’s on your nightstand?” Women mentioned male and female authors almost equally; men mentioned male authors more than 79 percent of the time. “Don’t read in bed,” advised Fran Lebowitz. “It’s too stimulating. Watch TV instead. It’s boring.”

In 2005 the British Cheese Board attempted to dispel the idea that eating cheese before bed causes nightmares. No evidence of this “evil myth” was reported among two hundred volunteers, though eating Stilton was found to lead to “crazy” dreams, while eating cheddar often led to dreams of celebrities. “We hope that people will think positively about eating cheese before bed,” said the board secretary.

Psychologists at the University of California recognized a lack of sleep “as a social repellent” and its effect contagious: “People who come in contact with a sleep-deprived individual, even through a brief one-minute interaction, feel lonelier themselves as a result.”