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dream is an unfolding sequence of perceptions, thoughts, and emotions that is experienced as a series of actual events during sleep. Key Questions How does brain activity change during dreaming sleep, and how are those changes related to dream content? What do people dream about, and why don’t we remember most dreams? How do the psychoanalytic, activation–synthesis, and neurocognitive models explain the nature and function of dreams? Dreams have fascinated people since the beginning of time. By adulthood, about 2 hours of a good night’s sleep is spent dreaming. Assuming you live to a ripe old age, you’ll devote 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—vague, thoughtlike ruminations about real events that usually occurs during NREM slow-wave sleep (McCarley, 2007). Sometimes, sleep thinking interferes with sleep, such as when anxious students toss and turn during the night before an important exam. In contrast to sleep thinking, a dream is an unfolding sequence of thoughts, perceptions, and emotions that typically occurs during REM sleep and is experienced as a series of real-life events (Domhoff, 2005a, 2005b). However bizarre the details or illogical the events, the dreamer accepts them as reality. In a recurring segment on The Late Late Show, celebrities read fans’ tweets describing their dreams about them, and they are often quite bizarre. In one episode, the Jonas Brothers read a fan’s description of her dream in which the Jonas Brothers were her cousins, and Nick Jonas asked to borrow money from her to buy tacos (Martin, 2020). To the fan, this dreamed event probably felt quite real. It was once thought that dreams occurred exclusively during REM sleep, but new research reveals that dreams also occur during NREM sleep (Foulkes & Domhoff, 2014; Siclari et al., 2017). 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 and fMRI scans reveal that the brain’s activity during REM sleep is distinctly different from its activity during either wakefulness or NREM slow-wave sleep (Fuller et al., 2006; Nofzinger, 2006). Dream Themes and Imagery 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. Most dreams are about everyday settings, people, activities, and events. In reviewing studies of dream content, researcher William 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. Analyzing thousands of dream reports, Domhoff (2007, 2011) found that negative feelings were more common than positive feelings. Apprehension and fear were the most frequently reported emotions, followed by happiness and confusion. Instances of aggression were more common than instances of friendliness, and the dreamer was more likely to be the victim of aggression than the aggressor. Women were more likely to experience emotions in their dreams, and men more likely to experience physical aggression. The emotional tone of the average dream pales in comparison with the intensity of a nightmare, a vivid and frightening or unpleasant anxiety dream that occurs during REM sleep. Nightmares often awaken 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). 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 et al., 2006). The Significance of Dreams Why do we dream? Do dreams contain symbolic or hidden messages? Three models of the nature and function of dreaming offer insights. Sigmund Freud: Dreams as Fulfilled Wishes Sigmund Freud believed that sexual and aggressive instincts are the motivating forces that dictate human behavior (see Chapter 1). Because these instinctual urges are so consciously unacceptable, sexual and aggressive thoughts, feelings, and wishes are pushed into the unconscious, or repressed. Freud believed that these repressed urges and wishes could surface in dream imagery. 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 swords and other elongated objects were phallic symbols, representing the penis, while cupboards and ovens 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 (Meltzer, 2018; 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 W. McCarley first proposed a new model of dreaming in 1977. Called the activation–synthesis model of dreaming, this theory maintains that brain activity during sleep produces dream images (activation), which are combined by the brain into a dream story (synthesis) (see Figure 4.4). Since it was first proposed, the model has evolved as new findings have been reported (see Hobson, 2017; McCarley, 2007). An illustration of a cross-section of the brain and brainstem. Activation - Synthesis Model of Dreaming. Signals are generated spontaneously in the brainstem. Curved arrows radiate out to multiple regions of the brain. Higher brain regions synthesize signals, imposing meaning on them. FIGURE 4.4 The Activation–Synthesis Model of Dreaming In the activation–synthesis model of dreaming, the brainstem produces signals for dream images (activation). The higher regions of the brain then impose some meaning on these dream images (synthesis), often in the form of a dream story. 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. 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 process stimuli from the external world. But rather than responding to 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. According to this model, then, dreaming is essentially the brain synthesizing and integrating memory fragments, emotions, and sensations that are internally triggered (Hobson et al., 1998, 2011). According to the activation–synthesis model, dream images are not symbols to be decoded. Rather, the meaning of dreams can be uncovered by understanding the deeply personal way the dreamer, once awake, makes sense of the chaotic progression of 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 (Foulkes & Domhoff, 2014; Siclari et al., 2017). 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 (Foulkes & Domhoff, 2014).