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Sleeping Yourself Smart
I mentioned at the beginning of the book that our brain’s deliberate system needs
to be well rested to function at its best. Sleep well, and you give your brain the
best chance of being able to marshal all of your intelligence when you need it.
Sleep badly, and you lose a few IQ points. Matthew Walker, who runs the Sleep
and Neuroimaging Lab at the University of California Berkeley, has conducted
several studies illustrating this stark truth. One experiment found that a solid
night’s sleep made people twice as effective at working out complex patterns in
information.
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In another experiment, people solved 30 percent more anagrams
after periods of rest that included rapid eye movement (REM) sleep—which we
get more of the longer we’re asleep.
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That’s not to say we can’t muster the energy to plow on when we’re
exhausted, as I’m sure you know all too well. As long as we’re only dealing with
familiar or predictable challenges, we can just about get by on autopilot.
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And if
we’re truly riveted by what we’re doing and are willing to put in extra mental
effort to stay focused, we can rally our deliberate system for a brief boost. But as
soon as we’re handling anything that isn’t either entirely routine or utterly
riveting—most of normal working life, in other words—we don’t have the
mental flexibility to perform at our best when we’re tired.
Moreover, we need decent sleep if we’re to make good use of what we
experience each day. Overnight, we move through several sleep cycles lasting
90–120 minutes, containing periods of light sleep, deep sleep, and REM sleep in
turn. Each type of sleep plays a slightly different role in helping us process our
experience of the world: reviewing the day’s events, recalling the things we’ve
learned, reinforcing neural pathways around new information to make it easier to
remember in the future, or connecting that new information to previously
encoded knowledge.
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A night’s sleep with plenty of those cycles leaves us with
a better chance that we’ll wake up with deeper understanding of what happened
the day before. A short night, meanwhile, means we create fewer long-lasting
memories and insights. In other words, we remember less and learn less.
Yet many of us persist in believing that it’s okay to burn the candle at both
ends. Everyone can imagine how a sleep-deprived driver might crash a vehicle,
but there’s a tendency to think that purely intellectual work is somehow immune.
Long nights remain common in some professions, because there’s a belief that
staying awake is better for meeting deadlines (and gaining badges of honor) than
getting some rest. But nobody’s immune to the workings of neurobiology. Big
errors of judgment get made. Andrew, an investment banker, told me about
mistakes he saw colleagues making when they’d been ordered to stay in the
office without sleep in the middle of big deals. “They were so exhausted that
they were sending sensitive emails and making calls to the wrong people, or
telling the buyer highly confidential things that they should have been telling the
seller, with disastrous results.”
Peggy’s learned to prioritize sleep, even when she’s up against a deadline.
“I’ll be working late to try to get something difficult done, and I’ll think, ‘I just
want to push through and finish this.’ But it’s not a recipe for good work. There
always comes a point where I know that if I got some sleep and then picked it up
in the morning, I’d nail it in a fraction of the time it’s taking me as I’m sitting
here, late and frustrated.”
Sometimes we intend to get a good night’s sleep, but we don’t make it easy
for our brains to get what they need. We all know the usual reasons we fall short
—long working hours, getting up early to get the kids ready, interminable
commutes—but an often overlooked cause is that many of us now use phones
and tablets in bed. This exposes us to light that’s rich in blue wavelengths,
something that makes our brains think it’s the middle of the day because it
suppresses melatonin, the hormone that signals to our brains that it’s time to
sleep. Naturally, that makes it harder for us to drop off. In fact, Harvard’s
Division of Sleep Medicine found that people’s bodies released melatonin a full
ninety minutes later when exposed to bright light rather than dim lighting before
bedtime—effectively shortening their night’s sleep by that long, too.
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Here are some suggestions on how to sleep smart:
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