A hundred years after Freud, one man may have figured out why we dream. You'll never think the same way about nightmares again.
By JAY Dixit published on November 01, 2007 - last reviewed on May 26, 2011
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
Say
you're in a fight and somebody wraps his arms around you from the
front, pinning your arms to your sides—a bear hug. Most people
reflexively stiffen their body. But this is actually the worst thing to
do; making your body rigid makes you easier to lift—and lets your
assailant pick you up and drop you on your head, or worse, haul you off
somewhere.
Better to bend your knees and lower your center of
gravity so you're harder to lift. You're then free to punch your
aggressor's testicles, claw the skin on his back, kick out his knee,
stomp his foot, even bite his neck—unappetizing options, but effective
against even the biggest thug.
The difference between the typical
and optimal response could save your life. But making such a reaction
swift and automatic takes practice. It's the reason martial arts
students drill their movements over and over. Frequent rehearsal
prepares them for that one decisive moment, ensuring that their response
in an actual life-or-death situation is the one they practiced.
Dreams
may do the same thing. A dream researcher at the University of Turku,
in Finland, Revonsuo believes that dreams are a sort of nighttime
theater in which our brains screen realistic scenarios. This virtual
reality simulates emergency situations and provides an arena for safe
training. As Revonsuo puts it, "The primary function of negative dreams
is rehearsal for similar real events, so that threat recognition and
avoidance happens faster and more automatically in comparable real
situations."