If the threat-simulation theory is correct, dreams should focus on the self, and when confronted with a threat, the dream self should react realistically to ensure its own survival and that of its loved ones. And so it is. We are the heroes of our own dreams. We don't dream about other people's adventures or about fictional superheroes battling monsters. We dream about ourselves.
If dreams evolved to simulate the threats in our environment, then being exposed to more dangers in real life should activate the nightmare function, overstuffing our dreams with threats. This is precisely what happens. Even a single exposure to a life-threatening situation can plunge a person into an inferno of post-traumatic nightmares, dreams in which the threatening event—the attack, the rape, the war—is repeated over and over in every possible variation.
Studies of traumatized Iraqi and Palestinian children who grew up in extremely violent environments, some of whom witnessed their parents' deaths, show that their dreams are phantasmagoric carnivals of threatening events. People who watched more television on September 11, 2001, and saw threatening images were more likely to dream about the events of that day; people who merely talked about it with others were less likely to dream about it.
Traumatic dreams do seem to rehearse relevant threats. Just four weeks into the first Gulf War, as Scud missiles were raining down on Tel Aviv and Haifa, the war was already encroaching on the dreams of Israeli college students, according to a study. The most prominent topic: gas masks.
But not all our dreams contain threats. That's not surprising, says Revonuso. There's no reason a biological system has to express its function at all times. Many bodily systems spring into action only in critical situations. Take sperm cells. The average man ejaculates over 100 million sperm at a time, yet over the course of his life, only a few will ever accomplish their biological mission of fertilizing an egg. Every day, millions of sperm are wasted—and while this may, as Monty Python sings, make God quite irate, it doesn't mean that sperm cells have some function other than fertilizing eggs and competing with other sperm.
The Nighttime Edge
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 Kekule 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, 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."
Tags:
burrow,
decathlon,
desert island,
drainage hole,
easy prey,
flowerpot,
instinctive reactions,
little desert,
millennia,
natural defenses,
nightfall,
ordeals,
paws,
rat society,
robbers,
uncomfortable position,
university of wisconsin at madison
