Dream

• 1. Introduction

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  A dream is a succession of dynamic scenes, ideas, emotions, and sensations that usually arrive involuntarily during certain stages of sleep. Humans spend more than two hours each night inside these private worlds. Each individual dream lasts only around 5-20 minutes. Yet for all the time we pour into dreaming, the most basic questions remain unanswered. Science cannot say where in the brain dreams originate. It cannot say whether there is a single origin or many regions involved. It cannot even say what dreaming is for. The study of dreams has its own name, oneirology, and modern researchers focus on the neurophysiology of dreams and on testing what function they might serve. But the puzzle stretches far past the laboratory. The content and meaning of dreams have drawn scientific, philosophical, and religious interest throughout recorded history. So how did ancient kings take orders from their sleep? Why does the most common emotion in a dream turn out to be anxiety? And what happens when two sleeping strangers manage to send each other a signal across the dark?

• 2. The Word Itself

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  In Old English, the word dream did not mean anything about sleep at all. It described noise, joy, or music. The sense we now take for granted, a series of thoughts, images, or emotions occurring during sleep, only attached itself to the word in the 13th century. Etymologists believe the shift was pushed by the Old Norse word draumr, which already carried the meaning the word dream holds today. So the term we use for our nightly visions was once a word for sound and celebration, and it had to borrow its sleeping sense from a Norse cousin before it became what it is now.

• 3. When Dreams Gave Orders

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  Gudea, king of the Sumerian city-state of Lagash, rebuilt the temple of Ningirsu because a dream told him to. He reigned around 2144-2124 BCE, and his building project came as a direct command from a dream figure. This was the ancient pattern. Writings from Mesopotamia and Ancient Egypt describe visitation dreams, where a deity or a prominent forebear appears and orders the dreamer to take specific actions, sometimes predicting events to come. In these dreams the sleeper was largely passive. Visual content mostly served to frame an authoritative voice, and the message arrived by hearing rather than seeing. Preserved writings from early Mediterranean civilizations record a relatively abrupt change between Bronze Age antiquity and the start of the classical era. After antiquity, the passive hearing of visitation dreams gave way to visualized narratives in which the dreamer becomes a character and actively participates. The degree to which dreams dictated waking behavior was sharply reduced in later millennia. The only trace of that old authoritative dream figure to survive into modern catalogues of dream characters is the inclusion of God among prominent persons.

• 4. What People Actually Dream

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  From the 1940s to 1985, Calvin S. Hall collected more than 50,000 dream reports at Western Reserve University. In 1966, Hall and Robert Van de Castle published The Content Analysis of Dreams, laying out a coding system to study 1,000 dream reports from college students. Participants from varying parts of the world showed striking similarity in their dream content. Hall's complete reports were made publicly available in the mid-1990s by his protégé William Domhoff, and more recent studies still cite the work favorably. In the Hall study, the most common emotion experienced in dreams was anxiety. Other emotions included abandonment, anger, fear, joy, and happiness, but negative feelings far outnumbered positive ones. The data showed that sexual dreams occur no more than 10% of the time and are more common in young to mid-teens. A separate study put sexual content at 8% of both men's and women's dreams. The visual texture of dreams is highly phantasmagoric, with locations and objects continuously blending into one another. The imagery generally reflects a person's memories and experiences, though conversation can take exaggerated and bizarre forms. People who are blind from birth do not have visual dreams; their dream contents draw instead on hearing, touch, smell, and taste. Outside events can reshape this inner landscape too. A study of over 15,000 dream reports by Deirdre Barrett found that during the COVID-19 pandemic, themes of fear, illness, and death became two to four times more prevalent than before its onset.

• 5. The Brain's Story Machine

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  Much dream research has succumbed to the law of the instrument. Studies detect an increase of blood flow in one brain region, then credit that region with generating dreams. Pooling results has led to a newer conclusion: dreaming involves large numbers of regions and pathways, likely different for different dream events. The tools available are limited. Most nations restrict human brain research to non-invasive procedures, and in the United States invasive procedures on a human subject are allowed only when surgically necessary for that same person's medical needs. Non-invasive measures like EEG voltage averaging or cerebral blood flow cannot pick out small but influential populations of neurons, and fMRI signals are too slow to explain how brains compute in real time. Animal subjects offer a workaround for some brain functions, but animal dreaming can only be inferred, never confirmed, so it yields no hard facts about dream neurophysiology. Examining humans with brain lesions provides clues, yet the lesion method cannot tell destruction apart from disconnection. One leading idea holds that dreams are stories the brain builds from scraps. Following their work with split-brain subjects, Gazzaniga and LeDoux proposed a left-brain interpreter that tries to create a plausible narrative from whatever signals reach the brain's left hemisphere. The textbook author James W. Kalat describes a dream as the brain's effort to make sense of sparse and distorted information, combining haphazard input with whatever else is occurring to synthesize a story. Neuroscientist Indre Viskontas is blunter, calling bizarre dream content just the result of your interpreter trying to create a story out of random neural signaling.

• 6. Theories Of Why

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  Robert, a physician from Hamburg, suggested in 1886 that dreams are a need, serving to erase sensory impressions and ideas not fully worked through during the day. Freud disputed this. His own dream studies focused on interpreting dreams rather than explaining how or why we dream, and he proposed that dreams preserve sleep by presenting troublesome wishes as already fulfilled. Dreams, he wrote, are the guardians of sleep and not its disturbers. A turning point came in 1953, when Science published the Aserinsky and Kleitman paper establishing REM sleep as a distinct phase and linking dreams to it. Many later studies meant to uncover dream function were in fact studying measurable REM sleep, not dreams; the Solms 2000 paper certified that the two phenomena are separable. Since the identification of REM sleep, the proposals have multiplied. Hobson and McCarley offered their 1977 activation-synthesis hypothesis, suggesting a role for dreaming sleep in promoting learning, and a 2010 Harvard study published experimental evidence correlating dreams with improved learning. Crick and Mitchison's 1983 reverse learning theory cast dreams as a computer's offline cleanup, removing junk from the mind. Hartmann proposed in 1995 that dreams serve a quasi-therapeutic function, letting the dreamer process trauma in a safe place. Revonsuo's 2000 threat simulation hypothesis held that dreams rehearse the physical and interpersonal threats that once endangered survival, and in 2015 he proposed social simulation theory, training social skills and bonds. Eagleman and Vaughn's 2021 defensive activation theory argues dreams keep the occipital lobe busy through the long darkness of sleep, protecting it from being claimed by other senses. Erik Hoel, drawing on artificial neural networks, proposes that dreams prevent overfitting to past experiences, helping the dreamer learn from novel situations.

• 7. Soul, Scripture, And Omen

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  J. W. Dunne argued that the idea of a soul first arose from primitive man observing his own dreams. Ignorant of any other explanation, Dunne wrote, he could conclude only that in dreams he left his sleeping body in one universe and went wandering into another, and that but for that savage the idea of a soul might never have occurred to mankind. The world's religions carry that logic forward. In the Mandukya Upanishad, part of the Veda scriptures of Hinduism, dreaming is one of three states the soul experiences, alongside waking and sleep. The earliest Upanishads, written before 300 BCE, stress two meanings: that dreams express inner desires, and that the soul leaves the body to be guided until awakened. In Judaism dreams can be interpreted for lessons, a subject discussed in the Talmud, Tractate Berachot 55-60. The ancient Hebrews, though monotheistic, distinguished good dreams from God and bad dreams from evil spirits, and incubated dreams to receive revelation. The prophet Samuel would lie down to sleep in the temple at Shiloh before the Ark and receive the word of the Lord. Joseph read a Pharaoh's dream of seven lean cows swallowing seven fat cows as seven bountiful years followed by seven of famine. Most of the dreams in the Bible appear in the Book of Genesis, including Jacob's dream of a ladder stretching from Earth to Heaven. The glossary Somniale Danielis, written in the name of Daniel, tried to teach Christian populations to interpret their dreams. Iain R. Edgar has researched dreams in Islam, where interpretation became the only path to revelation from God after the death of the last prophet, Muhammad. Islam classifies three types: the true dream, al-ru'ya, the false dream that may come from the devil, shaytan, and the meaningless everyday dream, hulm. In one narration by Aisha, the Prophet's dreams would come true like the ocean's waves. Dreams also drive conversion stories. According to ancient authors, Constantine the Great began his conversion to Christianity after a dream prophesied he would win the battle of the Milvian Bridge if he adopted the Chi-Rho as his battle standard.

• 8. Worlds Made And Doubted

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  Lewis Carroll built one of the best-known dream worlds in Alice's Adventures in Wonderland, and Looking-Glass Land in its sequel, Through the Looking-Glass. Unlike many invented dreamscapes, Carroll's logic mirrors actual dreams, with flexible causality and slippery transitions. Visual artists reached for dreams long before novelists settled the question of their meaning. In Renaissance and Baroque art, depictions often drew on Biblical narrative, with the Jacob's Ladder dream and St. Joseph's dreams especially favored. Later figures who depicted dreams include the Japanese woodblock artist Hokusai, who lived from 1760-1849, and the Western European painters Rousseau, Picasso, and Dalí. Doubt about which world is the real one runs just as deep. The first recorded version of the idea that the real world might be an illusion came in the 4th century BCE from Zhuangzi, and the problem carries his name as the Zhuangzi Paradox. He who dreams of drinking wine, Zhuangzi wrote, may weep when morning comes, and while a man dreams he does not know it is a dream, and may even try to interpret a dream within it. Only after waking does he know. Descartes formally introduced the same skeptical question to Western philosophy in the 17th century in his Meditations on First Philosophy.

  On the 12th of April 1975, a sleeping man moved his eyes left and right on purpose, and a scientist watching the signals knew exactly what it meant. The dreamer was Alan Worsley, and the watcher was psychologist Keith Hearne, who had recorded a communication from inside a lucid dream. A lucid dream is any dream during which the dreamer knows they are dreaming. Control over the dream's actions, characters, or environment can improve with practice, but it is not required for a dream to count as lucid, and the phenomenon has been scientifically verified. Those who lucidly dream are sometimes called oneironauts. Years after Hearne, psychophysiologist Stephen LaBerge extended the method, using eye signals to map the subjective sense of time in dreams, comparing brain activity during singing while awake and while dreaming, and studying in-dream sex, arousal, and orgasm. Researchers have even documented communication between two dreamers. Using EEG monitoring, ocular signaling, a red light stimulus, and a coordinating website, the system tracked when both people were dreaming. It sent the stimulus to one dreamer, who became lucid and signaled with eye movements; the website detected this and passed the stimulus along to the second dreamer, where it too was woven into the dream.