Dreams: Night School
A hundred years after Freud, one man may have figured out why we dream.
You'll never think the same way about nightmares again.
You'll never think the same way about nightmares again.
The Dream Robbers
What happens when a rat stops dreaming? In 2004, researchers at the University of Wisconsin at Madison decided to find out. Their method was simple if a bit devilish.Step 1:
Strand a rat in a tub of water. In the center of this tiny sea, allot the creature its own little desert island in the form of an inverted flowerpot. The rat can swim around as much as it pleases, but come nightfall if it wants any sleep, it has to clamber up and stretch itself across the flowerpot, its belly sagging over the drainage hole.
In this uncomfortable position, the rat is able to rest and eventually fall asleep. But as soon as the animal hits REM sleep, the muscular paralysis that accompanies this stage of vivid dreaming causes its body to slacken. The rat slips through the hole and gets dunked in the water. The surprised rat is then free to crawl back onto the pot, lick the drops off its paws, and go back to sleep—but it won't get any REM sleep.
Step 2:
After several mostly dreamless nights, the creature is subjected to a virtual decathlon of physical ordeals designed to test its survival behaviors. Every rat is born with a set of instinctive reactions to threatening situations. These behaviors don't have to be learned; they're natural defenses—useful responses accrued over millennia of rat society.
The dream-deprived rats flubbed each of the tasks. When plopped down in a wide-open field, they did not scurry to the safety of a more sheltered area; instead, they recklessly wandered around exposed areas. When shocked, they paused briefly and then went about their business, rather than freezing in their tracks the way normal rats do. When confronted with a foreign object in their burrow, they did not bury it; instead, they groomed themselves. Had the animals been out in the wild, they would have made easy prey.
The surprise came during Step 3. Each rat was given amphetamines and tested again; nothing changed. If failure to be an effective rat were due to mere sleep deprivation, amphetamines would have reversed the effect. But that didn't happen. These rats weren't floundering because they were sleepy. Something else was going on—but what?
What Dreams Are Made Of
Dreaming is so basic to human existence, it's astonishing we don't understand it better. It consumes years of our lives, and no other single activity exerts such a powerful pull on our imaginations. Yet central as dreaming is, we still have no idea why we dream. Freud saw dreams as convoluted pathways toward fulfilling forbidden aggressive and sexual wishes; frightening dreams were wishes in disguise—wishes so scary, he believed, they had to transmute themselves into fear and masquerade as nightmares.
Later came the idea that dreams are the cognitive echoes of our efforts to work out conflicting emotions. More recently, dreams have been viewed as mere "epiphenomena"—excrescences of the brain with no function at all, the mind's attempt to make sense of random neural firing while the body restores itself during sleep. As Harvard sleep researcher Allan Hobson puts it, dreams are "the noise the brain makes while it's doing its homework."
"There's nothing closer to a consensus on the purpose and function of dreaming than there's ever been," says Deirdre Barrett, a Harvard psychologist and editor of the forthcoming The New Science of Dreaming. Indeed, no theory has been able to reconcile the findings of various subdisciplines of dream science. Until now.
Finnish psychologist Antti Revonsuo believes the marooned rats lost their ability to defend themselves not because they were exhausted but because they were robbed of their dreams. Dreams, he contends, are a training ground in which animals and people alike go over the behaviors that are key to their survival. Prevented from dreaming, the rats were unable to rehearse their survival behaviors. In other words, they were defenseless because they were out of practice.
A Theater of Threats
Intriguing as Revonsuo's theory is, not everyone is sold on the idea that dreams are primarily a theater of threat rehearsal. Dream researchers have known for centuries that dreaming helps problem-solving, for example—but they still do not know why.Some researchers argue that dreams are designed specifically to help us come up with creative solutions. But if that's the case, it's infuriatingly inconsistent—and complicated by the fact that we rarely remember our dreams.
Those who awake with brilliant solutions to scientific or artistic problems are the exception. German chemist Friedrich August Kekulé struggled to find the molecular structure of benzene until he dreamed about a snake devouring its own tail and realized benzene was a closed circle—a ring. The self-taught Indian mathematician Srinivasa Ramanujan came up with every one of his proofs in dreams. Paul McCartney dreamed "Yesterday," woke up, and wrote it down.
Problem-solving may be a side effect of the simulation system. The mere fact of running scenarios over and over may inevitably generate new solutions. That's why when we have an important decision to make, we like to "sleep on it" first, why, according to a study by University of Maryland psychologist Clara Hill, couples who dream about their relationship are more likely to resolve their conflicts than couples who don't.
It's also known that we get better at tasks just by dreaming about them. Robert Stickgold, a sleep researcher at Harvard Medical School, has found that if you time people as they tap out the sequence 4-1-3-2-4 with their fingers, then ask them to do it again later that day, they are no better.
But let them sleep in between and their performance improves—literally overnight. The implication seems obvious: Sleep provides practice. People given brainteasers before bed dream about the answers. Math students are all too familiar with dreams about algebra problems. Anyone who's ever played too much Tetris knows you can start having Tetris dreams.
Stickgold holds that dreaming is much more complex than rehearsal. He points, for example, to the ability of sleep to allow us to integrate and consolidate knowledge. During sleep, our brains are making sense of the world, discovering new associations among existing memories, looking for patterns, formulating rules. "That's how we create meaning," says Stickgold. "Our brain puts things together."
Dreams do have a certain edge over conscious thought. Neuroimaging work has shown a distinct pattern of activation and inhibition in the dreaming brain. Visual and emotional centers are abnormally activated, while censoring mechanisms are deactivated. When we try to visualize during the day, imagery is thin and insubstantial, less real than the real world. But studies suggest that vivid hallucinations during dreaming rival the clarity and detail of vision itself.
"Dreaming is a sensitive system that tries to pay much attention to the threatening cues in our environment," Revonsuo concludes. "Their function is to protect and prepare us."
Yes," says Harvard's Barrett, "dreams are worrying about disasters. But they're also planning for nice things and they're fantasizing and they're problem-solving."
She contends that the purpose of dreaming is "as broad as all waking thought. That's why I say dreams are really just thinking in a different biochemical state."
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