Excellent question, but nobody knows for sure—at least not yet! Although many dream researchers believe that dreaming is functionally significant and may play a biological role, some argue that dreams are merely a by-product (a sort of epiphenomenon) of basic neurophysiological activity during sleep. That said, theories about the possible function of dreams abound. Among the most scientifically interesting ones are that dreams a) play a role in emotional regulation; b) help consolidate memories; and c) have an evolutionarily-based threat or social simulation function. In the end, dreaming may or may not have a function, but a multitude of findings show that dreaming is a unique and meaningful psychological product of the human brain. As such, dreams will continue to interest and challenge clinicians and researchers alike for years to come. Oh, by the way, what exactly is the function of wakefulness? :-)
Although I’ve long been fascinated by patterns of dream content (e.g., settings, characters, emotions, themes etc) that can be observed over a series of dreams, my interest in the field began with my own experiences with lucid dreaming. Other types of dreams that hold a particular fascination for me include nightmares, flying dreams, and recurrent dreams.
Although I’m convinced that many dreams are psychologically meaningful, I’m not a believer in “dream dictionaries” that say that dreaming of X means this and dreaming of Y means that. Based on my work both as a clinician and researcher, I think that when present, symbols and metaphors in dreams reflect the dreamer’s unique personality, way of thinking, interests, current concerns, and life experiences. For this reason, I’m a firm believer that to properly understand a dream, it is necessary to know the dreamer and, in an ideal world, to involve him or her in the process. I’m therefore highly sceptical of so-called “dream experts” who interpret dreams with little to no knowledge of the dreamer.
Studies of large samples of dream content collected in the laboratory as well as outside the laboratory show that dreams mostly occur in commonplace settings, contain a large number of familiar characters, and revolve around family concerns, love interests, and activities engaged in during waking life. In fact, only a minority of dreams involves unknown characters and activities that are out of the ordinary. So for the most part, dreams can viewed as a reasonable simulation of waking life characters, social interactions, activities, and settings.
Perhaps due to the highly visual nature of dreaming, people always have wondered if blind people dream. So what do we know? Questionnaire and lab studies show that people who are born blind or become blind before age 4 or 5 do dream even though they do not see images in their dreams. However, the dreams of blind people tend to contain much greater mentions of touch, taste and smell.. They are also much more likley to report sensory detials like surface textures (e.g., the edge of table was rough, as if it was unfinished), ambient temperature (e.g., the air was damp and cold), or the slope of a terrain (e.g., "the sidewalk was angled downward"). It is noteworthy that people who become blind after age 5 or 6 often retain visual imagery in their dreams, which suggests that there is a window for the development of the capacity to have visual dreams. More recent studies also suggest that blind people may experience more nightmares than the average person, possibly due to the greater risks they face (e.g., missing a step, being hit by a car) while navigating their daytime environments.
Although the overwhelming majority of dream reports contain visual and, to a lesser extent, kinesthetic elements, the presence of other sensory modalities has also been noted in both lab and home dream reports.Over 50% of dream reports contain auditory experiences while explicit references to olfactory, gustatory and pain sensations occur in less than 1% of all dream reports. One study found that women’s dream reports were more likely to contain olfactory or gustatory sensations whereas references to auditory and pain experiences occurred in a higher percentage of men’s dreams. That the more infrequent modalities of smell, taste and pain occur at all in dreams is an important demonstration of the representational capacities of dreaming.
Another excellent question. So what exactly is a lucid dream? Various definitions of the experience have emerged in the literature. The simplest of these states that lucid dreams are those in which the subject is aware that he or she is dreaming. Other researchers have added a qualifier: that one has to become perfectly or fully aware that one is dreaming. Exactly what is meant by the terms "perfectly" or "fully" is usually not explicitly stated, but usually involves the ability to consciously exert control over events in the dream scenery. It should be noted, however, that even though lucidity in dreams is often accompanied by varying degrees of dream control, this ability is not in itself a sufficient indicator of lucidity. A broader and more precise definition of what constitutes a lucid dream is given by Stephen LaBerge who suggests that the consciousness experienced by a lucid dreamer is not unlike that which is experienced during the waking state. Thus LaBerge writes that "the lucid dreamer can reason clearly, remember freely, and act volitionally upon reflection, all while continuing to dream vividly.” Similarly, Tart (1979) states that a lucid dream consists of more than just having the dreamer realize "This is a dream." Like LaBerge, he suggests that in a lucid dream "the 'higher' mental processes that we think of as characterizing waking consciousness, such as memorial continuity, reasoning ability, volitional control of cognitive processes, and volitional control of body actions (at least for the dream body), all seem to be functioning at a lucid, waking level.” Others have also adhered to this conceptualization of the lucid dream state.
It would appear then that the lucid dream experience may be best understood if placed on a continuum. At one end we would have what may be called low-level lucidity, in which an individual may realize that he or she is dreaming, but then wake up, or simply relapse into non-lucid dreaming. In the middle of the continuum would fall those lucid dreams in which the dreamer, in addition to knowing that he or she is dreaming, can also exert some degree of control over the dream environment and retain some but not all of his or her waking mental faculties. Thus a person in this situation may be able to move about in the dream scenery as he or she pleases, but may be unable to alter some aspects of the dream, remember what day it is, or remember what their agenda for the following day consists of. At the high end of the continuum are those dreams in which an individual can exert a considerable amount of control over the dream content and, most importantly, is in possession of his or her mental faculties to the same extent as if the person were fully awake.
To this continuum should also be added what Celia Green has termed "pre-lucid dreams" as well as the phenomenon of "false-awakenings." The former refers to those dreams "in which the subject adopts a critical attitude towards what he is experiencing, even to the point of asking himself 'Am I dreaming?' but without realizing that he is in fact doing so.” The latter refers to those dream experiences in which one dreams that one has woken up, usually in their normal sleep environment. Both of these phenomena are known to occur in lucid dreamers, especially novices.
In these past few years, there has seen a veritable explosion in the number of companies offering all kinds of substances (drugs, supplements) and devices (headgear, home EEG devices, gadgets delivering low doses of transcranial stimulation) to help people have lucid dreams. Although these products are widely marketed and often accompanied by strong claims about their success rates, little independent research has been conducted on their effectiveness. Moreover, there exist many self-training techniques that may give you better results. A clear-eyes look at these technologies for lucid dream induction can be found here in this excellent piece in NY Mag: http://nymag.com/scienceofus/2016/10/these-strange-gadgets-claim-to-teach-you-how-to-lucid-dream.html
If you’d like to learn more about self-training in lucid dreaming, you can read about some of these methods in this research article from our lab.
There is a growing appreciation among health specialists and the general public that nightmares are a frequent sleep problem with important consequences for sleep quality and mental health. Large student and community-based epidemiological studies across different countries indicate that 8% to 29% of adults report monthly nightmares while 2% to 6% report weekly nightmares. Community surveys assessing incidence of nightmare “problems” rather than frequency found that between 5% and 8% of the adult general population report a current problem with nightmares, while about 6% report a past problem.
Finally, one of our own studies based on almost 10 000 dream reports collected in home dream logs from over 550 participants showed almost 3% of all prospectively collected dream narratives were nightmares (very disturbing dreams that wake up the dreamer) while bad dreams (disturbing dreams which do not cause the dreamer to awaken; they are remembered only after being awakened by external factors such as an alarm clock or later during the day) accounted for almost 11% of the dream reports. Thus almost 15% of all remembered dreams are considered to be highly disturbing dreams.
The most frequent themes in nightmares are:
(1) physical aggression (threat or direct attack to one's physical integrity by another character, including sexual aggression, murder, being kidnapped or sequestered;
(2) interpersonal conflict (conflict-based interaction between two characters involving hostility, opposition, insults, humiliation, rejection, infidelity, lying, etc.);
(3) failure or helplessness (difficulty or incapacity of the dreamer to attain a goal, including being late, lost, unable to talk, losing or forgetting something, and making mistakes);
(4) Health-related concerns and death (presence of physical illness, disease, health-related concerns, or death of a character or of the dreamer);
(5) being chased (dreamer being chased by another character but not physically attacked);
(6) apprehension/worry (dreamer is afraid or worried about someone or something, without an objective threat being present);
(7) evil presence (seeing or feeling the presence of or being possessed by an evil force, including monsters, aliens, vampires, spirits, creatures, ghosts, etc);
(8) accidents (the dreamer or another character is involved in an accident, including vehicle accidents, drowning, slipping, falling, etc.);
(9) Disaster/calamity (plausible events ranging from relatively small scale anomalies such as a fire or flood in one's house or neighborhood to larger scale disasters such as earthquakes, war, the end of the world, etc);
(10) Insects/vermin (presence of or infestation, bites or stings from insects, rats, snakes, etc.)
The list above is based on a careful analysis of thousands of dream reports collected prospectively (for example, on daily dream logs) as opposed to asking people about the last nightmare they remember on a questionnaire. Themes of falling or being paralyzed appear infrequently in dream logs, but their high saliency makes them particularly memorable and thus more likely to be recalled in interviews or questionnaires long after their occurrence and many people can remember having one of these nightmares at least once in their lifetime, often many years ago. So nightmares of falling or being paralysed are certainly common in the sense that many people remembering having had such a nightmare at least once in their lifetime, but the themes above occur much more frequently over any given week, month, or year.
Also, it is important to bear in mind that themes of falling, being paralyzed, or suffocation may well represent other commonly experienced parasomnias such as hypnic jerks, isolated sleep paralysis, or sleep terrors. When faced with broadly defined questionnaire items, people may be more likely to report these types of sleep experiences as if they were nightmares. Providing subjects with clear definitions for nightmares as well as sleep terrors and requiring actual dream narratives to be reported in daily logs greatly reduces the inclusion of other sleep phenomena in these results.
Men’s nightmares were are more likely than women's to contain themes of disaster/calamity as well as of war and terror. In addition, themes of interpersonal conflicts are twice as frequent in women's nightmares than in men’s.
Although fear is the most frequently reported emotion in nightmares and bad dreams, almost half of all disturbing dreams contained primary emotions other than fear. These can include anger, sadness, and frustration. Also, we’ve published several studies showing that nightmares with these kinds of emotions are rated as being just as intense and disturbing as fear-driven nightmares. This is why the American Academy of Sleep Medicine defines nightmares as disturbing mental experiences rather than frightening dreams.
Another great question. I think one reason people think most dreams are bizarre is because those are the kinds of dreams we tend to share with others. If you wake up one morning and remember a dream where you were studying for an exam, or were stuck in traffic, or talking to some friends, you’ll likely not go out of your way to tell others. But, if while stuck in traffic a giant eagle grabbed your car in its talons and lifted you high above the city and flew you and your automobile across the sky, and then set you down by building where you work, then you may want to tell someone! Some people have also argued that by virtue of their unusual and salient nature, bizarre dreams are more likely to be remembered than their mundane counterparts.
There’s also the question of what we mean by bizarre. For instance, bizarreness can refer to likelihood of occurrence of the dream content in waking life, its degree of his adherence to natural laws, or to the presence of discontinuities and incongruities in the dream. Thus, dreaming of seeing someone hit by lightning is certainly unusual, but not bizarre in the sense of soaring through the air like a bird, or experiencing a sudden change in the dream setting (e.g., from being in a park to finding yourself back in a school from your childhood). And things can certainly be “off” in dreams, like seeing your best friend but realizing his voice is that of someone else, or that he inexplicably has no hair, or oddly long and crooked teeth.
That being said, studies of dream reports collected from laboratory and non-laboratory settings converge in showing that for the most part, dreams are a reasonable simulation of waking life in terms of characters, social interactions, activities and settings. Specifically, dreams typically contain the self from a first person perspective, take place in real and spatially coherent commonplace environments, tend to contain realistic recreations of familiar characters (e.g., family members, friends, colleagues) and similar to waking life, are nearly always organized around social interactions with others, including emotional and intellectual exchanges. Thus, contrary to older theories emphasizing bizarreness and disguise in dreams, modern dream research shows that a majority of dreams are best understood as simulations of life experiences that emphasize interpersonal and social interactions.
Of course, that is not denying that dreams can sometimes be very bizarre and that the dreams of some people are definitely stranger than the dreams of others.
I don’t know what your particular recurrent dream may signify, but several clinical dream theorists believe that recurrent dreams are related to unresolved life difficulties and that the cessation of a recurring dream indicates that the difficulty has been dealt with successfully. Consistent with these ideas, researchers have shown that the occurrence of recurrent dreams during adulthood is associated with stressors and lowered levels of psychological well-being and that the elimination of a previously recurrent dream is correlated with improved well-being. Thus, changes from recurrent to progressive dream patterns may be important indicators of how well people are adapting to life circumstances.
60% to 75% of adults report having had one or more recurrent dreams at some point in their lives. In some cases, recurrent dreams which emerge during childhood may persist into adulthood. There is also some evidence to indicate that recurrent dreams are more prevalent in women than they are in men.
In terms of dream content, 60% to 85% of recurrent dreams are described as being unpleasant. Dream content is described as being pleasant in approximately 10% of recurrent dreams, while the rest are rated as being either neutral or containing a mixture of both positive and negative emotions. . Because positive recurrent dreams occur infrequently, their association to measures of well-being has not been investigated. Thus, we do not know if people who report positive recurrent dreams also show a relative deficit on measures of well-being. Similarly, we do not know whether the maintained cessation of pleasant recurrent dreams is correlated with positive, negative, or no changes in well-being.
Themes in which the dreamer is in danger (e.g., threatened with injury, death, or chased) have been found to characterize approximately 40% of recurrent dreams from adulthood and between 65% and 90% of recurrent dreams recalled by adults from their childhood. Using the same broad content category, we showed that almost 80% of children’s recurrent dreams contain themes in which the dreamer was in danger. In a majority of these cases, the dreamer is often fleeing, attempting to hide, or helplessly watching events unfold.
Whereas threatening agents in adult recurrent dreams are typically human characters, children’s recurrent dreams are much more likely to contain monsters, wild animals, witches, zombies and other types of ghoulish creatures.
Several thematic content categories reported by adult are noticeably absent from children’s recurrent dreams. These included themes involving problems with house maintenance (e.g., the dreamer becomes overwhelmed by an inordinate number of household chores or discovers that the house is falling apart or in ruins), loosing one’s teeth, and being unable to find a private toilet.
As detailed in a paper I co-wrote with Dr. Nicholas Pesant, I believe that psychotherapists can be inspired by different, complementary ways of conceptualizing dreams and that working with dream material can be clinically helpful. There exist many approaches to working with dreams and, personally, I’ve never been a big fan of most psychoanalytically oriented approaches to dreamwork, including Freud's. I’m a much bigger fan of Jung’s conceptualization of dreams and think there exist many excellent (and integrative) approaches to dream work. These include the Dream Interview Method (DIM), elaborated by Delaney (1991), the cognitive-experiential model of dream interpretation developed by Hill (1996; 2003), and Ullman’s (1996) highly popular dream appreciation approach developed for group sessions. It should be noted that many dream researchers interested in dream work are adepts of Ullman’s method.
Putting specific approaches to dream work aside, a considerable body of clinical research suggest that clinical work with dreams can a) help clients gain insights about themselves, b) increase their involvement in therapy, c) facilitate access to issues that are central to clients’ lives, d) contribute to establishing a safe and trusting environment, and e) enrich the clinician’s understanding of the client’s dynamics and clinical evolution. That’s quite the list! Thus, when used judiciously and at the right time, dream work can certainly be a highly useful clinical tool.
In sum, there is strong evidence that clinicians have much to gain by attending to their clients’ dreams and that effective dream work is accessible to most clinicians. So dream interpretation may not be the royal road to the unconscious (or to better self-understanding), but is nonetheless a useful and effective road among others.
At the most general level, findings based on systematic content research (including several studies by our group) suggest that most dreams can be understood as simulations that enact the person’s main conceptions and concerns, including emotionally salient and interpersonal experiences. The Continuity Hypothesis of dreaming—one of the most widely studied models of dreaming—posits that dream content is psychologically meaningful in that it reflects the dreamer's current thoughts, concerns and salient experiences. The idea that dreams are generally continuous with these waking dimensions and drawn from many of the same psychological schemata that govern waking thought and behaviour also lies at the heart of many contemporary theories of dream function. This is true, for instance, for theories suggesting that dreaming plays a role in emotional regulation, that they serve to simulate waking reality, or that dreams reflect offline processing of recent events to help learning and guide future behaviour.
Findings from various studies are consistent with the view that dreams tend to reflect the contents of waking thoughts and concerns. For example, research has shown that the occurrence of unpleasant dreams (e.g., bad dreams and nightmares) in otherwise healthy adults is related to their levels of well-being, that dream content is reactive to the experience of naturalistic and experimental stressors, that some personality traits are correlated to specific dream content, that the topographical and sensory characteristics of dreams recalled by the congenitally blind are consistent with how they experience the world in waking-life, and that the social networks in dreams — that is, the pattern of direct and indirect relationships among the characters — have the same properties as the dreamer’s real life social networks. Furthermore, the fact that developmental contents of dreaming in children follow their developmental patterns in waking cognitive processes is also consistent with the view that dream and waking thought contents are continuous.
Indeed there are. Studies have found that people rarely dream of cognitively focused activities such as reading, writing, and computer-use, even if they engage in them for significantly long periods of time during the day. Similarly, some day-to-day activities and concerns such as commuting to work, eating, and financial worries rarely appear in dreams whereas the frequency of occurrence in dreams of social and interpersonal situations is not only very high, but also disproportional to the time spent thinking about such situations during wakefulness. There is also evidence showing that waking-life thoughts can have a greater impact on dream content than corresponding physical waking-life events. For example, thinking and fantasizing about sexual activities is more strongly related to the occurrence of erotic dreams than are actual waking-life experiences with sexual activities. Thus, dream content may be more continuous with waking-life thoughts than with actual waking-life events.
Questionnaire studies indicate that approximately 80% of adults answer positively to the question “Have you ever dreamed of sexual experiences?” with men reporting sexual dreams more often than women. The normative data from the classic HVDC studies indicates that 12% of men’ dreams and 4% of women’s dreams contained sexual content, including having or attempting intercourse, petting, kissing, sexual overtures and fantasies.
However, one study by our group of over 3500 dream reports found no gender differences, with approximately 8% of dream reports from both men and women containing sexually-related activity. The differences with the HVDC data may be partially due to sample composition (college students versus student and non-student adults).
Alternatively, it is also possible that women actually experience more sexual dreams now than they did 40 years ago, or that they now feel more comfortable reporting such dreams due to changing social roles and attitudes, or both.
While dreams often contain autobiographical memories (i.e., personal representations of times, places, associated emotions and other contextual knowledge) relatively few dream reports contain complete episodic memories (i.e., memories of personally lived experiences that reproduce places, actions and characters). However, people's experiences from the previous day (commonly known as day residues) remain the most frequent time referent depicted in dreams and occur in approximately half of all dream reports.
Now, getting to your question, studies on the temporal relationship between daily events and their incorporation into dreams have also revealed a temporal pattern known as the ‘dream-lag effect.’ This term refers to the high level of incorporation of events experienced 5 to 7 days prior to the dream. Hence, the temporal relationship between daily experiences and their subsequent incorporation in dreams can be defined by the day-residue effect (incorporation of material from the day immediately preceding the dream), as well as the dream-lag effect (incorporation into dreams of daytime experiences having occurred approximately one week prior to the dream). There exist other, more complex, temporal effects on dream content. You can read more about it here.
Although there were indications in early laboratory studies that dreaming occurs almost exclusively in REM sleep and that there were difference in the content of REM and NREM reports, many later studies suggest that the differences in recall are not black and white, especially late in the sleep period, and that some but not all of the content differences disappear when there is a control for word length (i.e., the number of words used to describe a given dream). Still, most studies conclude that dreams are more frequent and longer during REM periods and that many NREM reports seem to be “thoughts,” not dreams. In fact, NREM reports are more often a continuation of waking thoughts and memories, whereas there are few episodic memories in REM or home dream reports.
Although considerable research supports the continuity model of dreaming, central questions regarding the nature and extent of continuity between dreaming and wakefulness remain unanswered. For instance, it is still unclear what particular dimensions of waking life (e.g., physical activities, cognitions, emotions) are most robustly associated to specific dream content. Similarly, relatively little is known about the extent to which people's dreams are reactive to individual differences in waking state and trait variables (e.g., daily stressors, personality, psychological well-being). And, of course, there are many other models of how dream content relates to waking-life dimensions, including in terms of various kinds of learning, emotional regulation, how people react to different kinds of trauma, and so on.
Parasomnias are undesirable physical, behavioral or experiential phenomena that occur during entry into sleep, within sleep, or during partial arousals from sleep. Depending on their exact manifestations, frequency and intensity, parasomnias can be considered normal sleep phenomena, especially when occurring during childhood, and may not significantly impact sleep quality or quantity, or daytime functioning. While some parasomnias (e.g., recurrent isolated sleep paralysis, sleep-related groaning) may cause relatively little enduring distress, others (e.g., nightmares, REM sleep behavior disorder, sleepwalking, sleep terrors) can have significant consequences, including marked psychological distress, self injuries and sleep disruption in the patient and a mixture of concern and apprehension in family members.
Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, sleep paralysis, hypnagogic hallucinations (visual and/or auditory), and, in some cases, cataplexy or the sudden loss of muscle control. The disorder usually begins during childhood or adolescence and affects approximately 0.04% of the general population. Narcolepsy with cataplexy (known as type 1) is caused by the loss of hypocretin-producing neurons. Hypocretin is a peptide that plays a key role in the regulation of wakefulness (sleep/wake cycles).
Although the diagnosis of narcolepsy with cataplexy is relatively straightforward, the diagnosis of narcolepsy without cataplexy (type 2) can be challenging. While there’s currently no cure for the disorder, treatments involving lifestyle adjustments and pharmacologic options can greatly improve symptoms.
Very likley. Sleep paralysis is the inability to move any voluntary muscle at when falling asleep or from awakening (e.g., from REM sleep) while being subjectively awake and conscious (eyes open and aware of one’s surroundings). Episodes, which can be exceedingly frightening, may last a few minutes and subside either spontaneously or when interrupted by noise or other external stimuli. Sleep paralysis is often accompanied by fear, hypnagogic hallucinations, and intense feelings of realism. One review article of over 36 500 people found a lifetime prevalence rate of approximately 7.5% for the general population, 28% for students, and 32% for psychiatric patients. Other studies, however, suggest considerably higher prevalence rates in the general adult population.
Sleep paralysis can be accompanied bya range of distressing experiences that may involve visual, auditory, or tactile imagery. One of the most common and frightening example is felt presence experiences (i.e., the distinct sensation that another sentient being, human or not, is present in the room). The felt presence is usually perceived as terrifyingly malevolent. Episodes of sleep paralysis have been described throughout history and across cultures, giving rise to a rich and varied depiction of the experience itself as well as of the nature of these evil forces and presences.
Techniques for disrupting sleep paralysis include moving the extremities and self-monitoring (raising awareness, promoting calm) and there is evidence to suggest that attempting small movements (e.g., trying to wiggle one’s toes or fingers, blinking, moving one's tongue) is considerably more effective than trying to move one’s arms, legs, torso, or trying to get up or to scream.
If you’d like to know more about the history of sleep paralysis, you can check out this recent article from The Atlantic, or this online entry. Want more facts about sleep paralysis? You’ll find 7 of them here.
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