Why Sleep? Why Dream?
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Robert Lawrence Kuhn is the creator, writer and host of "Closer to Truth," a public television series and online resource that features the world's leading thinkers exploring humanity's deepest questions. Kuhn is co-editor, with John Leslie, of "The Mystery of Existence: Why Is There Anything at All?" (Wiley-Blackwell, 2013). This article is based on a "Closer to Truth" episode produced and directed by Peter Getzels and streamed at www.closertotruth.com. Kuhn contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

A friend who is suddenly sick asks that I drive him home on his motorcycle. I've never driven a motorcycle, the trip will take an hour on the highway, I have no helmet, and there's a second passenger. I ask if we could use surface streets; he says no. I ask what's the slowest speed we can go; he says 50 mph. I say I won't do it. Others crowd around, pressuring me to drive that bike. I say I'll order Uber and pay for everyone. I am smart enough to know that I should not drive that bike, but not smart enough to know that I am dreaming.

As I awake, I marvel. On the one hand, I was reasoning well, dealing rationally with complex ideas; on the other hand, I had no sense of basic reality. Both from the same brain at the same time. There is meaning here: what we assume to be a unified self is multiple mental faculties, each related to different brain areas or systems.

All my life I've been entranced by the brain. (I did a doctorate in brain research, and although I've done other things since, my passion for neuroscience and its implications has not dimmed). The brain is the mechanism by which we perceive the world — it's the most sophisticated organization of matter in the universe (as far as we know); it's matter aware of itself. Dreaming and sleeping, I suspect, are deep clues to human physiology and psychology. [7 Mind-Bending Facts About Dreams]

Start with sleep. When I'm tired, sleep is natural; but from an evolutionary perspective, sleep should be unexpected. To spend 6 to 8 hours a day unconscious — totally out — would make one vulnerable to pre-procreation death, an easy mark for hungry predators or social enemies. The ancient world was violent and brutish. Why, then, did evolution select for creatures that needed to sleep?

As for dreams, they have always mystified. All manner of folklore and superstition have arisen from dreams, as have innumerable religious experiences and perhaps whole religions. Some claim, even today, that dreams are windows into higher realities.

Sometimes sleep scares me. To go unconscious — to pass from being to nonbeing — seems astonishing. It's not that I fret not awaking up. It's that I'm awe-struck by the blankness before waking up, the sheer nothingness of my unconsciousness (in non-dream sleep). I'm obsessed by the mystery of consciousness, the opposite of blankness and nothingness. How does such subjective inner awareness come about?

One way to explore the mystery of consciousness is to investigate its absence, and sleep, in a sense, is the absence of consciousness. Another way is to examine altered states of consciousness — such as dreams. What might sleeping and dreaming reveal about consciousness?

The science of sleep and dreams

Robert Stickgold, a sleep researcher at Harvard Medical School, told me that when we sleep we're "doing as much work as when we are awake. It might turn out that, for every 2 hours our brain spends 'online' [i.e., awake], taking in new information, our brain needs an hour 'offline' [i.e., asleep], figuring out what it means." 

Stickgold said that our brains need to "go offline" — to tune out other information — so we can process internally the information we already have. The brain, he added, "shuts out external inputs, cuts off the outside world, so it can do what it needs to do."

The benefits of sleep apply not only to managing information in our brains but also to ensuring our body processes function optimally, Stickgold said. For example, a good night's sleep enables a vaccine to produce a good antibody response. There's evidence that insufficient sleep can alter insulin production (this might help explain the growing epidemic of obesity). And sleep seems to affect cognitive enhancement and emotional regulation. [5 Things You Must Know About Sleep ]

"I talk to pianists, who say, 'Bob, I was working on a Chopin étude and even after two hours of practicing I just couldn't get a three-line measure right,'" Stickgold explained. "'I went to bed, I got up the next morning, I sat down at the piano, and first time through, I had it perfectly.'"

Research confirms that sleep enables memory consolidation and thus learning, stimulates the immune system and thus fights disease, and regulates emotion and perhaps controls obesity. Continue without sleep and you will die. One can survive longer without food than without sleep.

What actually happens during sleep? There are two basic kinds or stages of sleep — REM (rapid eye movement sleep), during which we have our most intense dreams, and non-REM, when there is little brain activity and we are largely not dreaming (which to most people is sleep).

Evidence suggests that sleep — REM sleep, dreams, in particular — may facilitate creativity. 

Boston University neuroscientist Patrick McNamara told me "dreams are creative," explaining how "dreams take some basic elements, recombine them in unusual ways, and generate a radically different, counterfactual picture of the world."

To me, intense dreams feel more bizarre than creative. But according to McNamara, if you wake people during REM sleep and ask them to describe their dreams, the vast majority are creative, not bizarre, experiences.

Deirdre Barrett, a Harvard Medical School psychologist and dream researcher, agreed, citing for me well-documented instances of dreams solving actual problems that had seemed intractable. Favorable conditions include when there is a visual-spatial issue, where seeing something vividly reorients the problem, or when conventional wisdom is wrong and one needs to think outside the box. "Dreams have directly contributed to two Nobel prizes," Barrett noted.

Here's the big question about dreams: Are dreams meaningful in themselves, the way mystics and psychotherapists have imagined? Or are dreams the incidental byproducts of purely physiological functions of sleep?

And either way, can dreams stimulate creativity, perhaps by making strange connections and conjuring up bizarre ideas?

So, here's sleep, seemingly ordinary, but comprised of two radical elements: the utter blankness of non-consciousness and reality-bending, fantastical dreams.

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If you're a topical expert — researcher, business leader, author or innovator — and would like to contribute an op-ed piece, email us here.

The purpose of sleep and dreams

I went to the University of Cambridge to visit Nicholas Humphrey, an English psychologist who explains consciousness via evolution. "Dreams are a form of play and serve the same functions as ordinary play in waking life," Humphrey told me. "This allows us to experiment with alternative realities in a safe environment. We can play doctors and nurses, or cowboys and Indians, all sorts of games, adult games too, in which we take on roles that we've never experienced before."

"We play even more so at night," Humphrey hypothesized, "in the theater of our dreams, completely safe. … Nature sees to it that we paralyze our bodies from the neck down so we don't act out our dreams — and then we can fly, we can fight, we can make love, or do whatever it may be, in completely new kinds of situations, with new people, or with old people, friends who have no idea how we're exploiting them in our dreams."

Sleep, Humphrey said, is "a sort of little death, and what this 'death' tells us is that we survive it: we go to sleep — our consciousness is obliterated, we are obliterated — but, sure thing, next day, we recreate ourselves. And this is such a regular occurrence that, of course, we just take it for granted, but it is a kind of miracle — we lose consciousness and then out of nothing it all comes back again."

"It's like a kind of Big Bang. The universe created out of nothing. We repeat that every day when we wake up."

Summing up, why sleep? Good health and good thinking. 

Why dream? Some say creativity and adaptability — to swim with the strange, to play without harm, to enter the mind of others. But to others, dreams are just byproducts of brain biology, mere nocturnal housekeeping.

Was sleep required in evolution? To lose consciousness with predators prowling would seem a weak adaptation, not given to prolific offspring. Perhaps, though, sleep strengthens the waking state.

Because we lose consciousness, some call sleep the little death. And because we always awake after sleep, some believe that we will likewise awake after death. 

But as an argument for life after death, I'm afraid, the analogy between sleep and death falls short.

Sleep as a window on the wonders of consciousness? That I like better. By experiencing blankness, we appreciate awareness.

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