A long time ago humans would sleep during the day when they were exhausted. Whenever their bones ached from making candles or joining wood they laid down or slumped over and slept. They woke up when they weren't tired anymore, and picked up their work where they left off. Guess what? Our forebears were fucking irresponsible when it came to dozing. Thanks to the miracle of science, we now know that taking naps isn't some bullshit Rockwellian surrender but a complex exercise that demands all our faculties.

The Wall Street Journal immediately smacks the chewed-up blanky from our hands:

"Naps are actually more complicated than we realize," said David Dinges, a sleep scientist at the University of Pennsylvania's Perelman School of Medicine. "You have to be deliberative about when you're going to nap, how long you're going to nap and if you're trying to use the nap relative to work or what you have coming up."

Pop quiz, hot shot: You stayed up all night working on those graphics for the slideshow on cloud-based log management start ups and now you're so tired you can barely operate the finger puppet props for your HuffPost Live segment on rainwater-powered needle exchanges. Think you can just duck under your cubicle for a quick lunchtime siesta? Maybe, if you're a total shithead.

For a quick boost of alertness, experts say a 10-to-20-minute power nap is adequate for getting back to work in a pinch.

For cognitive memory processing, however, a 60-minute nap may do more good, Dr. Mednick said. Including slow-wave sleep helps with remembering facts, places and faces. The downside: some grogginess upon waking.

Finally, the 90-minute nap will likely involve a full cycle of sleep, which aids creativity and emotional and procedural memory, such as learning how to ride a bike. Waking up after REM sleep usually means a minimal amount of sleep inertia, Dr. Mednick said.

Good luck confidently looking Arianna in the eye with only 23 minutes of NREM sleep. But oh, you say, you're the type who can dive deep into REM at the drop of your chin. You're "totally awesome at power naps." You actually think this helps you? In your fucking dreams (which you shouldn't be having).

A telltale sign of being very sleep-deprived, he said, is dreaming during a short nap. "Definitely in a 20-minute nap you should not be dreaming," [Dr. Mednick] said.

These are serious sleep decisions in serious times, which requires serious sleep firepower so you can adequately wrestle your convulsing brain to the ground and beat the shit out of it to get that healing rest you deserve.

Christopher Lindholst, chief executive and co-founder of New York-based MetroNaps, has installed specially designed sleeping pods for Google, Huffington Post, an Iowa construction company and the Arizona Diamondbacks baseball team. The chairs retail for $8,995 to $12,985.

Too poor to make such a crucial investment in your health? Thankfully, WSJ offers a DIY tip for cowards.

Another trick to waking up perky after a short nap is to drink a cup of coffee before sleeping. Caffeine won't hurt such a short break and should lessen the effect of sleep inertia.

People who have sleep inertia are worthless assholes. In unrelated news, productivity is sky-high but wages continue to nosedive.