KEY THEME

A dream is an unfolding sequence of perceptions, thoughts, and emotions that is experienced as a series of actual events during sleep.

KEY QUESTIONS

Dreams have fascinated people since the beginning of time. By adulthood, about 25 percent of a night’s sleep, or almost two hours every night, is spent dreaming. So, assuming you live to a ripe old age, you’ll devote more than 50,000 hours, or about six years of your life, to dreaming.

Although dreams may be the most interesting brain productions during sleep, they are not the most common. More prevalent is sleep thinking, also called sleep mentation. Sleep thinking usually occurs during NREM slow-wave sleep and consists of vague, bland, thoughtlike ruminations about real-life events (McCarley, 2007). Sometimes, sleep thinking interferes with sleep, such as when anxious students toss and turn, reviewing terms and concepts during the night before an important exam.

In contrast to sleep thinking, a dream is an unfolding sequence of perceptions, thoughts, and emotions during sleep that is experienced as a series of real-life events (Domhoff, 2005a, b). However bizarre the details or illogical the events, the dreamer accepts them as reality.

Most dreams happen during REM sleep, although dreams also occur during NREM (Domhoff, 2011). When awakened during active REM sleep, people report a dream about 90 percent of the time, even people who claim that they never dream. The dreamer is usually the main participant in these events, and at least one other person is involved in the dream story. But sometimes the dreamer is simply the observer of the unfolding dream story.

People usually have four or five dreaming episodes each night. The first REM episode of the night is the shortest, lasting only about 10 minutes. Subsequent REM episodes average around 30 minutes and tend to get longer as the night continues. Early morning dreams, which can last 40 minutes or longer, are the dreams most likely to be recalled.

PET (positive-emission tomography) and fMRI scans have revealed that the brain’s activity during REM sleep is distinctly different from its activity during either wakefulness or NREM slow-wave sleep (Fuller & others, 2006; Nofzinger, 2006). These differences and the roles they play in dream content are explored in the Focus on Neuroscience box, “The Dreaming Brain.”

Although almost everyone can remember having had a bizarre dream, research on dream content shows that bizarre dream stories tend to be the exception, not the rule. As dream researcher William Domhoff (2007) points out, dreams tend be “far more coherent, patterned, and thoughtful than is suggested by the usual image of them.” Most dreams are about everyday settings, people, activities, and events. Common, however, are abrupt scene changes and unusual juxtapositions of images and actors.

In reviewing studies of dream content, Domhoff (2005b, 2010) has concluded that so-called common dream themes, like being naked in a public place, flying, or failing an exam, are actually quite rare in dream reports. And, dream emotions are usually appropriate in the context of the dream story (Domhoff, 2011). Based on studies of thousands of dream reports, Domhoff (2007, 2011) has identified the following common themes:

If apprehensive or fearful emotions become progressively more intense as a dream story unfolds, the person may experience a nightmare. A nightmare is a vivid and disturbing dream that often awakens the sleeper. Typically, the dreamer feels helpless or powerless in the face of being aggressively attacked or pursued. Although fear, anxiety, and even terror are the most commonly experienced emotions, some nightmares involve intense feelings of sadness, anger, disgust, or embarrassment (Nielsen & Zadra, 2005).

Nightmares are most common in childhood, but about 5 to 10 percent of adults report that they experience nightmares at least weekly. Women report more frequent nightmares than men. Daytime stress, anxiety, and emotional difficulties are often associated with nightmares. As a general rule, nightmares are not indicative of a psychological or sleep disorder unless they occur frequently, cause difficulties returning to sleep, or cause daytime distress (Levin & Nielsen, 2007; Nielsen & others, 2006).

Why do we dream? Do dreams contain symbolic or hidden messages? In this section, we will look at three models of the nature and function of dreaming. We’ll start with the most famous one—the psychoanalytic explanation proposed by Sigmund Freud.

SIGMUND FREUD: DREAMS AS FULFILLED WISHES

In the chapters on personality and therapies (Chapters 11 and 15), we’ll look in detail at the ideas of Sigmund Freud, the founder of psychoanalysis. As we discussed in Chapter 1, Freud believed that sexual and aggressive instincts are the motivating forces that dictate human behavior. Because these instinctual urges are so consciously unacceptable, sexual and aggressive thoughts, feelings, and wishes are pushed into the unconscious, or repressed. However, Freud believed that these repressed urges and wishes could surface in dream imagery.

In his landmark work, The Interpretation of Dreams (1900), Freud wrote that dreams are the “disguised fulfillments of repressed wishes” and provide “the royal road to a knowledge of the unconscious mind.” In fact, he contended that “wish-fulfillment is the meaning of each and every dream.” According to the psychoanalytic view of dreaming, then, dreams function as a sort of psychological “safety valve” for the release of unconscious and unacceptable urges (see Yu, 2011).

Freud (1904) believed that dreams have two components: the manifest content, or the dream images themselves, and the latent content, the disguised psychological meaning of the dream. For example, Freud (1911) believed that dream images of sticks, swords, brooms, and other elongated objects were phallic symbols, representing the penis. Dream images of cupboards, boxes, and ovens supposedly symbolized the vagina.

In some types of psychotherapy today, especially those that follow Freud’s ideas, dreams are still seen as an important source of information about psychological conflicts (Auld & others, 2005; Pesant & Zadra, 2004). However, Freud’s belief that dreams represent the fulfillment of repressed wishes has not been substantiated by psychological research. Furthermore, research does not support Freud’s belief that the dream images themselves—the manifest content of dreams—are symbols that disguise the dream’s true psychological meaning (Domhoff, 2003, 2011).

THE ACTIVATION-SYNTHESIS MODEL OF DREAMING

Researchers J. Allan Hobson and Robert McCarley first proposed a new model of dreaming in 1977. Called the activation-synthesis model of dreaming, this model maintains that dreaming is our subjective awareness of the brain’s internally generated signals during sleep. Since it was first proposed, the model has evolved as new findings have been reported (see McCarley, 2007; Pace-Schott, 2005). Hobson’s most recent model, called the Activation-Input-Modulation (AIM) Model, is a more comprehensive attempt to relate dreaming to waking awareness with specific reference to the balance of neurotransmitters (Hobson, 2009).

According to the activation-synthesis model, dreams occur when brainstem circuits at the base of the brain activate and trigger higher brain regions, including visual, motor, and auditory pathways (see FIGURE 4.6). As noted earlier in the Focus on Neuroscience box “The Dreaming Brain,” limbic system structures involved in emotion, such as the amygdala and hippocampus, are also activated during REM sleep. When we’re awake, these brain structures and pathways are involved in registering stimuli from the external world. But rather than responding to stimulation from the external environment, the dreaming brain is responding to its own internally generated signals (Hobson, 2005).

In the absence of external sensory input, the activated brain combines, or synthesizes, these internally generated sensory signals and imposes meaning on them. The dream story itself is derived from a hodgepodge of memories, emotions, and sensations that are triggered by the brain’s activation and chemical changes during sleep. According to this model, then, dreaming is essentially the brain synthesizing and integrating memory fragments, emotions, and sensations that are internally triggered (Hobson & others, 1998, 2011).

The activation–synthesis theory does not contend that dreams are completely meaningless. But if there is a meaning to dreams, that meaning lies in the deeply personal way in which the images are organized, or synthesized. In other words, the meaning is to be found not by decoding the dream symbols, but by analyzing the way the dreamer, once awake, makes sense of the progression of chaotic dream images.

THE NEUROCOGNITIVE THEORY OF DREAMING

In contrast to the activation-synthesis model, the neurocognitive model of dreaming emphasizes the continuity between waking and dreaming cognition. According to William Domhoff (2005a, 2010, 2011), dreams are not a “cognitive mishmash” of random fragments of memories, images, and emotions generated by lower brainstem circuits, as the activation-synthesis model holds. Rather, dreams reflect our interests, personality, and individual worries (Nir & Tononi, 2010).

Further, the activation-synthesis model rests on the assumption that dreams result from brain activation during REM sleep. However, as Domhoff and other dream researchers point out, people also dream during NREM sleep, at sleep onset, and even experience dreamlike episodes while awake but drowsy (Nir & Tononi, 2010).

Like dreams, Domhoff (2011) notes, waking thought can also be marked by spontaneous mental images, rapid shifts of scene or topic, and unrealistic or fanciful thoughts. Thus, dreams are not as foreign to our waking experience as the activation-synthesis model claims. Instead, dreams mirror our waking concerns, and do so in a way that is remarkably similar to normal thought processes.