Brain Rules (Updated and Expanded)

Are you a lark, owl, or hummingbird?
Each of us wages this war on a slightly different schedule. The late
advice columnist Ann Landers apparently would take her phone off the
hook between 1:00 a.m. and 10:00 a.m. Why? This was the time she
normally slept. “No one’s going to call me,” she said, “until I’m ready.” The
cartoonist Scott Adams, creator of the comic strip 
Dilbert
, never would
think of starting his day at 10:00 a.m. “I’m quite tuned into my rhythms,”
he told the authors of 
The Body Clock Guide to Better Health
. “I never try
to do any creating past noon. … I do the strip from 6:00 to 7:00 a.m.” Here
we have two creative and well-accomplished professionals, one who starts
working just as the other’s workday is finished.
About one in 10 of us is like 
Dilbert
’s Adams. The scientific literature
calls such people larks (more palatable than the proper term, “early
chronotype”). In general, larks report being most alert around noon and feel
most productive at work a few hours before they eat lunch. They don’t need
an alarm clock, because they invariably get up before the alarm rings—
often before 6:00 a.m. Larks cheerfully report their favorite mealtime as
breakfast and generally consume much less coffee than non-larks. Getting
increasingly drowsy in the early evening, most larks go to bed (or want to
go to bed) around 9:00 p.m.
Larks are incomprehensible to the one in 10 humans who lie at the other
extreme of the sleep spectrum: “late chronotypes,” or owls. In general, owls
report being most alert around 6:00 p.m., experiencing their most
productive work times in the late evening. They rarely want to go to bed
before 3:00 a.m. Owls invariably need an alarm clock to get them up in the
morning, with extreme owls requiring multiple alarms to ensure arousal.
Indeed, if owls had their druthers, most would not wake up much before

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10:00 a.m. Not surprisingly, late chronotypes report their favorite mealtime
as dinner, and they would drink gallons of coffee all day long to prop
themselves up at work if given the opportunity. If it sounds to you as though
owls do not sleep as well as larks in American society, you are right on the
money. Indeed, late chronotypes usually accumulate a massive “sleep debt”
as they go through life.
Whether lark or owl, researchers think these patterns are detectable in
early childhood and burned into genes that govern our sleep/wake cycle. At
least one study shows that if Mom or Dad is a lark, half of their kids will be,
too. Larks and owls, though, cover only about 20 percent of the population.
The rest of us are called hummingbirds. True to the idea of a continuum,
some hummingbirds are more owlish, some are more larkish, and some are
in between.
Nappin’ in the free world
It must have taken some getting used to, if you were a staffer in the
socially conservative early 1960s. Lyndon Baines Johnson, 36th president
of the United States and leader of the free world, routinely closed the door
to his office in the midafternoon and put on his pajamas. He then proceeded
to take a 30-minute nap. Rising refreshed, he would then resume his role as
commander in chief. Such presidential behavior might seem downright
weird. But if you asked a sleep researcher like Dement, his response might
surprise you: It was LBJ who was acting normally. The rest of us, who
refuse to bring our pajamas to work, are the abnormal ones.
LBJ was responding to something experienced by nearly everyone on
the planet. It goes by many names—the midday yawn, the post-lunch dip,
the afternoon “sleepies.” We’ll call it the nap zone, a period of time in the
midafternoon when we experience transient sleepiness. It can be nearly
impossible to get anything done during this time, and if you attempt to push
through, which is what most of us do, you can spend much of your
afternoon fighting a gnawing tiredness. It’s a fight because the brain really
wants to take a nap and doesn’t care what its owner is doing. The concept of
“siesta,” institutionalized in many other cultures, may have come as an
explicit reaction to the nap zone.

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At first, scientists didn’t believe the nap zone existed except as an
artifact of sleep deprivation. That has changed. We now know that some
people feel it more intensely than others. We know it is not related to a big
lunch (although a big lunch, especially one loaded with carbs, can greatly
increase its intensity). We also know that when you chart the process S
curve and process C curve, you can see that they flatline in the same place
—in the afternoon. The biochemical battle reaches a climactic stalemate.
An equal tension now exists between the two drives, which extracts a great
deal of energy to maintain. Some researchers, though not all, think this
equanimity in tension drives the need to nap. Some think that a long sleep at
night and a short midday nap represent default human sleep behavior, that it
is part of our evolutionary history.
Regardless of the cause, the nap zone matters, because our brains don’t
work as well during it. If you are a public speaker, you already know it is
darn near fatal to give a talk in the midafternoon. The nap zone also is
literally fatal: More traffic accidents occur during it than at any other time
of the day.
If you embrace the need to nap rather than pushing through, as LBJ
found, your brain will work better afterward. One NASA study showed that
a 26-minute nap reduced a flight crew’s lapses in awareness by 34 percent,
compared to a control group who didn’t nap. Nappers also saw a 16 percent
improvement in reaction times. And their performance stayed consistent
throughout the day rather than dropping off at the end of a flight or at night.
(The flight crew was given a 40-minute break, it took about six minutes for
people to fall asleep, and the average nap lasted 26 minutes.) Another study
showed that a 45-minute nap produces a similar boost in cognitive
performance, a boost lasting more than six hours. Also, napping for 30
minutes before pulling an all-nighter keeps your mind sharper in the wee
hours.
What happens if we don’t get enough sleep
Given our understanding of how and when we sleep, you might expect that
scientists would have an answer to the question of how much sleep we
need. Indeed, they do. The answer is: We don’t know. You did not read that
wrong. After all of these centuries of experience with sleep, we still don’t

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know how much of the stuff people actually need. Generalizations don’t
work. When you dig into the data on humans, what you find is not
remarkable uniformity but remarkable individuality. To make matters
worse, sleep schedules are unbelievably dynamic. They change with age.
They change with gender. They change depending upon whether or not you
are pregnant, and whether or not you are going through puberty. One must
take into account so many variables that it almost feels as though we’ve
asked the wrong question.
So let’s invert the query. How much sleep