Brain rule 7 from John Medina is “sleep well, think well.”

“Methought I heard a voice cry, “Sleep no more!
Macbeth does murder sleep,” the innocent sleep,
Sleep that knits up the ravell’d sleave of care,
The death of each day’s life, sore labour’s bath,
Balm of hurt minds, great nature’s second course,
Chief nourisher in life’s feast…

Will Shakespeare probably knew something about not getting enough sleep, and his language here is apt. Sleave is not a misspelling, but a synonym for skein. Macbeth imagines sleep as repairing the day’s mental tangles and twists.

A tale of two processes

Medina notes that the brain doesn’t rest in the way our muscles do. In fact, there’s a kind of ongoing struggle between two mental armies: one under the banner of the circadian arousal system (“process C”) and the other, the homeostatic sleep drive (“process S”).

Studies of people isolated from clocks and cues like sunlight confirm that humans tend to follow a roughly 24-hour pattern, with the process C (the wake state) lasting about twice as long as process S (sleeping). The amount of sleep an individual needs varies greatly from one person to the next — and with gender, and with age. So Medina suggests inverting the question and asking, “How much sleep don’t you need?”

Inadequate sleep can greatly decrease mental functioning. In one study, “when sleep was restricted to six hours or less per night for just five nights… cognitive performance matched that of a person suffering from 48 hours of continual sleep deprivation.”

Larks and owls

Many people have an optimal time of day, even with adequate sleep. 10% of the population consists of larks, or if you prefer, “early chronotypes.” They’re up before the alarm, often drink less coffee, and are ready for bed by about 9 p.m.

Late chronotypes (“owls”) make up about 20% of the population, which make explain why many of us are so puzzled by larks. Many owls say they’re most alert around 6 p.m., and if given the choice wouldn’t sleep till about 3 a.m.

There’s a side effect to the recurring combat between process C and process S. About midway through our day, no matter when we start it, both processes seem to run down — as if the two opposing armies are exhausted.

This midafternoon drag isn’t related to big lunches (though a high-carb lunch can make the sleepiness more intense). One thought is that a midday nap was an evolutionary adaptation — enabling our early ancestors to restore their alertness and abilities for the second half of the day.

What to do? Take a nap.

Medina cites a NASA study showing that a 26-minute nap improved a pilot’s perforamnce by 34%, and refers to other studies with similar effects. If you prefer anecdotes, many people known as indefatigable workers — Lyndon Johnson, Winston Churchill — regularly took naps. (Churchill is also patron saint of the owls.)

As with naps, so with nighttime sleep. Medina reports an intriguing experiment involving students and math problems. The students learned a method for solving the problems, but were not told about a shortcut that could solve them faster.

If twelve hours passed between the initial training and a second set of problems, about 20% of the group would have discovered the shortcut… but if that twelve hours included eight hours of sleep, the discovery rate rose to 60%. “No matter how many times the experiment is run, the sleep group consistently outperforms the non-sleep group about 3 to 1.”

Some ideas that Medina muses about (while admitting they need further research):

• Matching chronotypes among workers. In other words, don’t make an owl the partner of a lark.
• Promote naps. Those of us who don’t work in an office have a better opportunity to embrace this idea, but even in an organizational setting, you can mimimize the effect of the nap zone by avoiding meetings, presentations, or critical work during the lull. A NASA scientist asked, “What other management strategy will improve people’s performance 34% in just 26 minutes?”
• Sleep on it. Allow a night’s sleep between your initial encounter with the details of some problem and your attempt to resolve it.

Lark Motel photo by Thomas Hawk;
owl coffee photo by Neil101 / Neil Wilkinson.