Excerpt adapted from The Promise of Sleep (1999) by permission of Delacorte Press. Copyright © 1999 by William C. Dement.
I used to be a very heavy smoker. What started as an occasional indulgence in my Army days had, by the early 1960s, become chain smoking. One day in 1964, I was coughing into a handkerchief and noticed with a chill that the little flecks of sputum on the white cloth were reddish pink. I sought out a radiologist friend and asked him to order a chest X ray. The next day I went back to his office, full of dread. I will never forget the grim expression on his face as he motioned me to the light box behind his desk. Without a word, he turned and clipped my chest film onto it. Immediately I saw that my lungs harbored a dozen white spots -- cancer. A wave of anguish and despair overwhelmed me. I could barely breathe. My life was over. I wouldn't see my children grow up. All because I hadn't stopped smoking, even though I knew all about smoking and cancer. "You utter fool," I thought. "You've destroyed your own life!"
And then I woke up.
The bloody sputum, the X rays and the cancer had been a dream -- an incredibly vivid dream. What a relief. I was reborn. I had been given the chance to experience inoperable lung cancer without having it. I stopped smoking right then and have never lit another cigarette.
To some, it may seem amazing that people will take drastic action as a result of something that didn't even happen. But the emotional impact of dreams can be so powerful that they might as well have really occurred. The logical part of the awake brain knows that the dream was not real, but to the emotional part of the brain, what we dream really happens to us.
Many people consider dreams the most important part of sleep. It was dreams that first attracted me to the science of sleep, and decades later I remain fascinated by their power and mystery. However, there is a controversy raging among sleep researchers. Recent research by prominent neuroscientists purports to show that dreams are nothing more than random nerve activity in the brain, with no real purpose or meaning. I think they can signify much more.
The idea that dreams hold a personal message for the dreamer has a long history. Early this century Freud revived interest in the interpretation of dreams, systematically looking beyond their conscious or manifest content to find a latent content, which he felt usually involved repressed sexual feelings or other taboo impulses. The "safe" (disguised) release of these impulses of violence, incest and primitive orality allows people to stay sane, Freud believed. Although the idea that dreams are a "safety valve" preventing psychosis is no longer widely accepted by sleep researchers, belief in the significance of dreams has become increasingly common among the lay public.
Some people try to interpret a dream by looking at "dream books," which are always vague and useless. These nonsense books might tell you, for instance, that a dream of ice represents "frozen emotions." Yet for Eskimos, ice may symbolize the world at large; or for people who live in the desert, it may represent the exotic. Cigars may symbolize a phallus, a capitalist, a nuisance -- or, as Freud said, sometimes just a cigar. I believe there are personal messages to be found in dreams, possibly even ideas that the conscious mind represses; however, their meaning depends very much on the individual and his or her cultural context.
Some anthropologists accept the idea that common dream objects and actions can have similar meanings to people in the same culture. Some dreams are so widespread in Western culture that their meaning is taken for granted. For instance, the dream of being naked in public is usually associated with dreamers' fears of being seen for who they really are. Dreams of taking tests or missing lectures are common anxiety dreams. Dreams of trying to get somewhere and being foiled again and again often occur when dreamers have some ambivalence about actually getting somewhere or doing something. Wish-fulfillment dreams might come in the form of a personal visit from a favorite movie star. Usually you wake up from one of these dreams and know exactly what it means. Even if you couldn't articulate it, you would know it held some significance.
And you would be dead wrong, according to a post-Freudian school of thought that is at the heart of one of the debates raging at the frontier of neuroscience and psychology. A few of today's most prominent sleep scientists -- aided by a range of technologies from EEG machines to PET scans -- have concluded that dreams do not reveal our true thoughts and emotions.
In the early 1970s, two prominent Harvard sleep researchers, J. Allan Hobson and Robert McCarley, found that during rapid-eye-movement (REM) sleep, a small area near the brain's base creates strong, regular bursts of nerve signals. These signals travel upward and spread throughout the cortex, where most of the brain's higher functions take place. The two scientists studied cats but postulated that similar bursts occur during REM sleep in all animals, including humans. Hobson and McCarley -- psychiatrists who are also eminent neurophysiologists -- propose that these bursts are the source of dreams. According to their "activation-synthesis hypothesis," the bursts originating in the area called the pons, at the base of the brain, "activate" nerve cells throughout the brain, bringing forth images, sensations and feelings.
Dreams result, they say, when the brain does what it does every day in waking life: makes sense of incoming nerve signals. The idea is that the brain takes what is essentially random, meaningless nerve activation and "synthesizes" something that has some meaning and coherence, even if it has to resort to making up its own story. Accordingly, there is no hidden meaning in dreams. Sensations in dreams, the Harvard researchers say, are much like the sensations experienced when scientists painlessly stimulate brain sections at random with an electrical probe. When one part of the brain is stimulated, the subject may report hearing music. When another part is probed, the subject remembers a childhood toy. The sensations or memories the person experiences depend on which nerve cells the probes happen to hit. These two scientists propose that the thoughts and memories that emerge in dreams are also the result of random nerve excitation. The superficial content of dreams, they believe, is the whole content; there is no need for finding hidden meanings.
Many people cannot accept these conclusions. Psychoanalysts, of course, find heretical the idea that dreams are merely a random collage of thoughts and images. Even though Freud and his theories have faded from center stage, there is still a widespread belief that dreams do have some profound messages for us.
I believe that the struggle between neuroscience and psychoanalysis has yielded a false dichotomy. The question is not whether all dreams are pointless or all dreams are profound. First, we do not know for certain if the same process observed in the base of cats' brains operates during REM sleep in humans. It is also possible that once the pons gets the dream process going, the dream may, in effect, take on a life of its own within the more complicated human brain. Finally, some dreams may be without purpose or meaning, while others may be quite the opposite.
In addition, we have to distinguish between meaning and purpose. If you were looking up at the clouds and saw a formation that suggested a familiar face, then that face would have meaning for you. The face might make you think of an old friend. It might even change the course of your life, if you then contacted that friend and became close again. However, it would be absurd to say that the cloud purposefully took its shape to give you the experience of seeing the face. In the same way, dreams of a familiar person or a menacing figure can have very personal meaning for you without having a functional purpose, such as to relieve stress or to express hostility.
I would take my argument even further. What we have learned about the brain since the 1970s suggests that the activation-synthesis theory ought to be modified. Random bursts of nerve activity may be continuously produced in the base of the brain, but the nerve signals' pathways will not be nearly so random by the time they reach the cortex. Over time, as the brain's nerve cells are used, they change their behavior. If they have been stimulated, the cells may become more reactive. If you have been frightened during the day, the nerves that control the startle response and feelings of fear will be more reactive that night. So, as these random signals of a dream travel through the brain, they are modified and filtered by the brain's current state. And because the state of the brain is created by your experiences, dream images and feelings are real reflections of your experiences.
To understand what I mean, think of a stained-glass window. White light, which is a jumble of all colors, enters on one side, but what comes out on the other side has a definite pattern of colors that is often very meaningful. Like the stained-glass window (a filter for light), the brain acts as a filter that imposes order on the random signals passing through it.
All of this does not close the door on the idea that dreams do represent truly unconscious thoughts. Unconscious thoughts have as much opportunity as conscious ones to modify the state of the brain and shape nerve signals passing through.
I think that is what happened in my smoking dream. Clearly, the overriding significance of this dream was that it altered my behavior, bringing about a difficult change that some people cannot accomplish even at the expense of their lives and health. But there was probably even more to it than that. At that time, I was smoking a great deal and worrying about the accumulating evidence that smoking causes cancer. In addition, I felt a lot of internal conflict because I was spending nearly every night away from home in the lab, sleeping during the day and leaving my wife to care for our three young children. My life was, in a way, upside down. I don't think I repressed these feelings -- I was conscious of the problems and worried about them -- but I did try to ignore the implications of my smoking and overwork. The neurological activity of the cancer dream dredged up these psychological conflicts and presented them in a way that I couldn't ignore, leading me to resolve the problems in my life.
Current neuroscience also can help explain how some images in a dream can be many things at once -- a phenomenon Freud called condensation. For instance, it is common for people to say about a dream, "I was talking to my father, but he was also Fred, my teacher." Or they might say, "I was holding an apple, but it was also a book, because I began to read it." The truth is that we don't have one neuron that gets activated when an apple is in front of us. When the image of an apple passes from the eyes into the brain, it activates the constellation of neurons that represent the color red, spherical objects, common fruits and the like.
When initial signals in the brain are not coming from a real apple, but rather from a random generator in the brain stem, it is possible for objects to have qualities that they usually don't. For instance, if the right constellation of nerves is activated, an object could have all the qualities of both a "real" book and a "real" apple, although this is physically impossible (and difficult even to imagine in our waking moments).
I hope the future of dream study will yield greater accessibility to our dream world -- allowing our waking selves to have more access to our dreams and our dreaming selves to have more access to our waking life. As I think back to my cancer dream, it strikes me that heightened reality within dreams could offer some great insights. I used to wish that Soviet and American leaders and generals would dream about an all-out nuclear exchange and have the experience of slowly dying on a planet bereft of civilization -- the so-called nuclear winter. I also have imagined that we might supplement our learning and training in the waking state by studying and practicing in the dream world.
Ultimately, the real importance of thoroughly understanding dreams may be learning how the brain works, how we perceive and why we think the way we do. We cannot help but create worlds in our minds to make sense of whatever neurological signals are buzzing about the brain. We may find that dreaming and being awake have much more in common than we thought. As the writer Havelock Ellis noted: "Dreams are real while they last -- can we say more of life?"
William C. Dement, MD, founded the world's first sleep disorders center at Stanford in 1970. A professor of psychiatry, he teaches the undergraduate course, Sleep and Dreams. Christopher Vaughan is a science writer living in Palo Alto.