Dream glossary: terms from sleep and dream research

Glossary

Short definitions of the terms these pages use. Each one stands on its own, and where a term has a page of its own, the entry links to it.

Activation-synthesis hypothesis: The activation-synthesis hypothesis is a theory of dreaming proposed by the psychiatrists J. Allan Hobson and Robert McCarley in 1977. It holds that during REM sleep the brainstem sends largely random signals to the forebrain, which then synthesises them into the images and stories we experience as dreams. Hobson later revised the model, and many researchers now give dream content more meaning than the original version allowed.See Why do we dream? The science of dreaming, explained
Anima and animus: Anima and animus are archetypes in the analytical psychology of Carl Jung. Jung described the anima as the feminine side of a man's unconscious and the animus as the masculine side of a woman's, often appearing in dreams as a figure of the other sex who guides, tempts or challenges the dreamer. Many later Jungians apply the ideas more flexibly and no longer tie them strictly to gender.See Jungian archetypes in dreams: the shadow, the anima and animus, the threshold
Archetype: An archetype, in the theory of Carl Jung, is an inherited, universal pattern in the human psyche that shapes how we imagine and respond to recurring situations, such as the mother, the hero, the trickster or the wise old figure. Jung held that archetypes surface in dreams, myths and religions across cultures. The idea is influential in psychotherapy and the humanities but has not been established by experimental research.See Jungian archetypes in dreams: the shadow, the anima and animus, the threshold
Cognitive behavioural therapy (CBT): Cognitive behavioural therapy is a structured, usually time-limited form of psychotherapy that works on the links between thoughts, feelings and behaviour. Developed from the 1960s, notably by the psychiatrist Aaron Beck, it teaches people to notice unhelpful thinking patterns and test them against evidence. It has a large research base for depression, anxiety disorders and insomnia, and imagery rehearsal therapy for nightmares is one of its techniques.
Collective unconscious: The collective unconscious is Carl Jung's term for a deep layer of the psyche that he believed all humans share, as distinct from the personal unconscious built from an individual's own forgotten or repressed experience. In Jung's theory it contains the archetypes and explains why similar motifs appear in the dreams and myths of unrelated cultures. It remains a theoretical concept rather than an empirical finding.See Jungian archetypes in dreams: the shadow, the anima and animus, the threshold
Continuity hypothesis: The continuity hypothesis is the proposal that the content of dreams reflects the concerns, relationships and activities of the dreamer's waking life. It is associated with the content analysis work of Calvin Hall and, later, researchers such as G. William Domhoff and Michael Schredl. Studies that code large numbers of dream reports have repeatedly found support for it, although dreams rarely replay waking events exactly.See Why do we dream? The science of dreaming, explained
Dream incubation: Dream incubation is the practice of deliberately focusing on a question, person or theme before sleep in the hope of dreaming about it. It has ancient roots, for example in the Greek temples of Asclepius, where the sick slept in search of healing dreams. Modern studies show that presleep suggestion can influence what people dream about, but not that incubated dreams deliver reliable answers.
Dream journal: A dream journal is a written or recorded log of dreams, ideally made immediately on waking, before the memory fades. Entries usually note the content, the feelings, the people and places in the dream and the date. Keeping one tends to increase how many dreams a person recalls, and over weeks it shows recurring figures, settings and emotions that single dreams cannot reveal.See What a dream journal is and how to keep one
Dream recall: Dream recall is the ability to remember dreams after waking, usually measured as how many dreams a person reports per week or month. It varies widely between people and from week to week. Recall tends to be better when someone wakes directly out of REM sleep, has an interest in dreams, intends to remember them and writes them down at once, before moving or thinking about the day.See How to remember your dreams
False awakening: A false awakening is a dream in which the dreamer believes they have woken up, often in their own bedroom, and begins the ordinary routine of the morning while still asleep. It can repeat several times in a row before real waking. False awakenings are often reported alongside lucid dreams and sleep paralysis, and noticing an odd detail is one way dreamers realise they are still dreaming.See Lucid dreaming: the basics
Hall and Van de Castle system: The Hall and Van de Castle system is a method for coding the content of dream reports, published by the psychologists Calvin Hall and Robert Van de Castle in 1966. It counts elements such as characters, social interactions, emotions, settings, objects, misfortunes and successes, and compares the results with published norms. It is the most widely used coding system in dream research and has been automated in recent studies.
Hypnagogia: Hypnagogia is the transitional state between wakefulness and sleep, at sleep onset, in which many people experience brief, vivid images, sounds, voices or bodily sensations known as hypnagogic hallucinations. They are common and usually harmless. The matching state on waking is called hypnopompic. Frequent, frightening hallucinations together with heavy daytime sleepiness are worth mentioning to a doctor, since they can accompany narcolepsy.
Hypnic jerk: A hypnic jerk is a sudden, involuntary twitch of the muscles that happens as a person is falling asleep, often together with a feeling of falling or a brief image, and sometimes waking them with a start. It is very common and considered harmless. Hypnic jerks tend to be more frequent with caffeine, stress, intense exercise in the evening and sleep deprivation.
Imagery rehearsal therapy (IRT): Imagery rehearsal therapy is a cognitive behavioural treatment for chronic nightmares. While awake, the person writes down a recurring nightmare, changes it in any way they choose, and then rehearses the new version in imagination for a few minutes each day. It is one of the best-studied psychological treatments for nightmares, including those after trauma, and is recommended in clinical guidelines for nightmare disorder.See Nightmares and imagery rehearsal therapy
Individuation: Individuation is Carl Jung's term for the lifelong psychological process by which a person becomes a whole and distinct individual, by bringing unconscious parts of the personality, such as the shadow and the anima or animus, into relationship with consciousness. Jung saw dreams as one of the main ways this process shows itself. It is a central concept of Jungian analysis, not a measurable stage of development.See Jungian archetypes in dreams: the shadow, the anima and animus, the threshold
Lucid dream: A lucid dream is a dream in which the dreamer knows, while it is happening, that they are dreaming. Some lucid dreamers can also steer events in the dream, though awareness and control do not always come together. Surveys suggest that about half of people have had at least one, and laboratory studies have confirmed lucidity during REM sleep using agreed eye-movement signals.See Lucid dreaming: the basics
MILD (mnemonic induction of lucid dreams): MILD, short for mnemonic induction of lucid dreams, is a technique for inducing lucid dreams developed by the psychophysiologist Stephen LaBerge around 1980. On waking from a dream, the person recalls it, repeats an intention such as "next time I am dreaming, I will remember that I am dreaming", and imagines becoming lucid in that dream before falling asleep again. It is usually practised after waking briefly in the early morning.See Lucid dreaming: the basics
Nightmare: A nightmare is a vivid, disturbing dream, usually arising from REM sleep in the second half of the night, whose fear, anger, sadness or disgust typically wakes the dreamer, who then remembers it clearly. Occasional nightmares are common at every age and especially in childhood. They differ from night terrors, which arise from deep NREM sleep and are usually not remembered.See Nightmares and imagery rehearsal therapy
Nightmare disorder: Nightmare disorder is a sleep disorder recognised in the DSM-5 and the international classification of sleep disorders, in which repeated, well-remembered, intensely distressing dreams cause significant distress or impair daytime life, mood or sleep. On waking the person quickly becomes alert and oriented. It is common after trauma, treatable, most often with imagery rehearsal therapy, and should be assessed by a doctor or psychologist.See Nightmares and imagery rehearsal therapy
NREM sleep: NREM sleep, short for non-rapid eye movement sleep, makes up most of a night's sleep and is divided into three stages, from light sleep in N1 and N2 to deep, slow-wave sleep in N3. Deep NREM sleep is concentrated in the first half of the night. People woken from NREM sleep also report dreams, though these tend to be shorter and more thought-like than REM dreams.
Reality testing: Reality testing, in lucid dreaming practice, is the habit of checking several times a day whether you are awake or dreaming, for example by reading a line of text twice, looking closely at your hands or trying to breathe through a pinched nose. The aim is for the habit to carry into dreams, where the check fails and reveals the dream. Psychiatry uses the same phrase in a different sense.See Lucid dreaming: the basics
Recurring dream: A recurring dream is a dream that returns with the same or nearly the same content over months or years. Studies suggest that 60 to 75 percent of adults have had at least one, and most are unpleasant, often involving being chased, trapped, falling or being unprepared. Research links them to stress and unresolved concerns, and they tend to fade when the underlying situation changes.See Recurring dreams: what psychology says
REM rebound: REM rebound is the increase in the amount and intensity of REM sleep that follows a period in which REM sleep was reduced, for example after sleep deprivation, after stopping alcohol or certain medications such as many antidepressants, or after a disrupted night. It often brings unusually vivid or intense dreams and sometimes nightmares. Changes to prescribed medication should be discussed with a doctor first.
REM sleep: REM sleep, short for rapid eye movement sleep, is the stage of sleep in which the eyes move quickly under closed lids, brain activity resembles wakefulness and most skeletal muscles are temporarily paralysed. It was described by Eugene Aserinsky and Nathaniel Kleitman in 1953. It returns roughly every 90 minutes, lengthens towards morning, and is the stage from which the most vivid, story-like dreams are reported.
Shadow: The shadow, in the psychology of Carl Jung, is the part of the personality that a person does not recognise or accept as their own, including traits they find shameful and also undeveloped strengths. Jung held that it often appears in dreams as a threatening or despised figure of the dreamer's own sex. In his theory, facing the shadow is an early step of individuation.See Jungian archetypes in dreams: the shadow, the anima and animus, the threshold
Sleep paralysis: Sleep paralysis is a brief state, on falling asleep or waking, in which a person is conscious but cannot move or speak, because the muscle paralysis of REM sleep continues into wakefulness. It can come with a sense of a presence in the room, pressure on the chest or vivid hallucinations. Episodes last seconds to minutes and are harmless in themselves; frequent ones are worth raising with a doctor.
Threat simulation theory: Threat simulation theory is an evolutionary theory of dreaming proposed by the Finnish psychologist Antti Revonsuo in 2000. It holds that dreaming evolved to simulate threatening events, so that the brain could rehearse perceiving and avoiding danger, which would have aided survival in ancestral environments. It draws support from how often dreams contain threats, but whether dreaming has this function remains debated.See Why do we dream? The science of dreaming, explained
Typical dream: A typical dream is a dream theme that large numbers of people report across ages and cultures, such as being chased, falling, flying, losing teeth, being late, sitting an exam or being naked in public. Researchers including Tore Nielsen have measured how common these themes are with questionnaires. Their frequency shows shared human concerns, not that a given theme has one fixed meaning for everyone.