Dream

Based on Wikipedia: Dream

Every night, you become a filmmaker, a novelist, and a madman all at once. For more than two hours while you sleep, your brain conjures entire worlds—vivid landscapes that melt into one another, conversations with people living and dead, stories so strange that waking life could never produce them. And then, almost always, you forget everything by breakfast.

Dreams are one of the oldest mysteries of human experience. We spend roughly a third of our lives sleeping, and a significant chunk of that time dreaming, yet we still cannot say with certainty why we dream at all.

What Happens When You Dream

A dream is a succession of images, scenes, emotions, and sensations that occur involuntarily during sleep. Each dream typically lasts between five and twenty minutes, though it might feel much longer when you're inside one. The experience is almost always visual for people who can see—a kind of private cinema where you're simultaneously the audience, the director, and the lead actor.

The visual quality of dreams is what scientists call phantasmagoric. That's a delightfully spooky word meaning that different locations and objects blend continuously into each other without the logical transitions we expect in waking life. You might be in your childhood kitchen, and then suddenly you're on a mountain, and the mountain is also somehow your office, and none of this seems strange until you wake up.

People who have been blind from birth don't experience visual dreams. Their dreamscapes are built from other senses—sounds, textures, smells, tastes. The brain works with whatever sensory material it has available.

The most common emotion in dreams is anxiety. Not joy, not wonder, not even fear exactly—anxiety. Studies analyzing thousands of dream reports have found that negative emotions significantly outweigh positive ones. We spend our sleeping hours more often worried than happy, which seems rather unfair.

Sexual dreams, despite what popular culture might suggest, occur in only about eight to ten percent of dreams. They're more common during adolescence and can occasionally result in what are colloquially called "wet dreams"—orgasms or nocturnal emissions during sleep.

The REM Connection

Dreams happen primarily during a phase called rapid eye movement sleep, abbreviated R-E-M and typically written as REM. During REM sleep, your brain activity looks remarkably similar to when you're awake, even though your body is essentially paralyzed. Your eyes dart around beneath closed lids—hence the name—as if watching something unfold.

The discovery of REM sleep in 1953 by researchers Eugene Aserinsky and Nathaniel Kleitman was a turning point for dream science. Before that paper appeared in the journal Science, dreams were studied mainly through the lens of interpretation—what do they mean?—rather than mechanism—how do they happen?

But here's what's fascinating: dreams don't occur only during REM sleep. You can dream during other sleep phases too, and not every REM period produces dreams that you remember. The link between REM and dreaming is strong but not absolute.

Because many animals exhibit REM sleep—essentially all mammals do—scientists have speculated that animals dream too. Your dog twitching and whimpering during sleep might well be chasing dream rabbits. But we can never know for certain. To study a dream, someone must wake up and describe it. A dream that can't be reported might as well not exist, at least for scientific purposes. This means we can't confirm dreaming in animals, human fetuses, or babies who haven't learned to speak.

The Word Itself

The English word "dream" has a strange history. In Old English, the word drēam meant noise, joy, or music—nothing to do with sleeping visions. It wasn't until the thirteenth century that English speakers started using "dream" for what happens during sleep, probably influenced by the Old Norse word draumr, which had that meaning all along.

So for centuries, English speakers used an entirely different vocabulary for their nighttime experiences. The medieval mind dreamed, but they didn't call it that.

Ancient Dreams Were Different

If you could travel back four thousand years and ask someone in ancient Mesopotamia or Egypt about their dreams, you would hear about a radically different experience than what we report today.

In the ancient world, dreams were primarily about receiving messages. These were called visitation dreams, and they followed a recognizable pattern: a divine figure or important ancestor would appear and deliver instructions or prophecies. The dreamer was passive, a recipient rather than a participant. The visual content was secondary—what mattered was what the dream figure said.

Consider Gudea, king of the Sumerian city-state of Lagash, who ruled around 2144 to 2124 before the common era. He rebuilt the temple of Ningirsu because a dream told him to. This wasn't metaphorical or symbolic. The dream gave direct orders, and the king obeyed.

Compare this to modern dream reports, where dreamers are active characters in visual narratives. We don't passively receive divine commands; we participate in stories, often absurd ones. The shift from hearing to seeing, from receiving to experiencing, represents a profound change in how humans relate to their dream lives.

Nobody knows exactly when or why this transition happened, but preserved writings suggest it occurred relatively quickly between the Bronze Age and the classical Greek period. Something changed in how humans dreamed—or at least in how they understood and reported their dreams.

The Science of Dream Content

From the 1940s through 1985, a psychologist named Calvin Hall collected more than fifty thousand dream reports at Western Reserve University. In 1966, Hall and his colleague Robert Van de Castle published a systematic way to analyze dream content, studying a thousand dreams from college students.

What they found was surprising: people around the world dream about remarkably similar things. The cast of characters, the emotional tone, the types of situations—these show up consistently across cultures. Dreams are deeply personal, yet somehow also universal.

The only echo of those ancient visitation dreams in modern reports is occasional appearances of God or other prominent figures. But these are rare, appearing in a small category alongside celebrities and historical figures. The commanding deity who once dominated human dream life has become a minor character.

More recently, the global pandemic demonstrated how outside events shape our inner worlds. A study of over fifteen thousand dream reports found that themes of fear, illness, and death became two to four times more common after the COVID-19 pandemic began. We process our anxieties in sleep, even when we'd rather escape them.

Where Dreams Come From

We don't know where in the brain dreams originate. That sentence is worth reading twice, because it represents an extraordinary gap in our understanding of ourselves.

We know dreams involve visual processing areas, emotional centers, memory systems. Brain imaging shows increased blood flow to various regions during REM sleep. But pooling all these studies together leads to an unsatisfying conclusion: dreaming seems to involve large numbers of brain regions and pathways, likely different ones for different types of dream experiences. There's no "dream center" we can point to.

The problem is partly technological. The tools we have for studying human brains—techniques like electroencephalography and functional magnetic resonance imaging—are either too imprecise or too slow to capture the moment-by-moment neural activity that produces a dream. And ethical rules rightfully prevent scientists from inserting electrodes directly into healthy human brains to find out.

Animal studies can't help much either. We can examine rat brains with much greater precision, but since we can't confirm that rats dream or ask them what they experienced, any findings are speculation at best.

The Interpreter in Your Head

One compelling theory comes from research on patients whose two brain hemispheres have been surgically separated—the so-called split-brain patients. Scientists Michael Gazzaniga and Joseph LeDoux proposed that the brain's left hemisphere contains something like an interpreter, a storytelling module that tries to create coherent narratives from whatever signals reach it.

During waking life, this interpreter receives orderly information and produces sensible stories. But during REM sleep, many brain regions are only partially active, sending fragmentary and distorted signals. The interpreter does its best with this chaotic input, weaving together whatever arrives into something resembling a plot.

This would explain why dreams feel meaningful while you're having them but often seem bizarre upon waking. The interpreter doesn't care if the story makes sense by daylight logic; it just needs to impose some narrative structure on the noise. As neuroscientist Indre Viskontas puts it bluntly, dreams are "just the result of your interpreter trying to create a story out of random neural signaling."

This theory is elegant but perhaps too dismissive. Dreams often incorporate recent memories, unresolved problems, emotional preoccupations. They're not entirely random. Something is selecting which signals get through and how they combine.

Why We Dream: Competing Theories

If we don't know how dreams happen, we're even less certain about why. Theories abound, each capturing something true without explaining everything.

The oldest idea is that dreams are messages—from gods, from the unconscious, from some external source of wisdom. Ancient Egyptians believed dreams were the best way to receive divine revelation. They practiced dream incubation, sleeping in special sanctuaries on designated "dream beds" hoping for guidance from the gods.

Sigmund Freud, the father of psychoanalysis, proposed that dreams are guardians of sleep. Wishes that would otherwise wake us up are represented as fulfilled in dreams, allowing sleep to continue. You're thirsty, so you dream of drinking, and you don't wake up to get water. Freud was less interested in why we dream than in what dreams mean, but his theory at least suggested a function.

In 1977, researchers Allan Hobson and Robert McCarley proposed the activation-synthesis hypothesis, suggesting that dreams play a role in learning and memory consolidation. A 2010 Harvard study provided experimental support, showing that people who dreamed about a task they had learned performed better at it afterward.

Francis Crick—yes, the DNA co-discoverer—teamed with Graeme Mitchison in 1983 to propose that dreams are like a computer's cleanup operations. During sleep, the brain removes parasitic connections and neural junk that accumulated during the day. You dream of forgetting, essentially, and what you remember is just the debris.

Antti Revonsuo's threat simulation hypothesis, proposed in 2000, takes an evolutionary approach. For most of human history, physical and interpersonal threats were constant dangers. People who practiced dealing with threats in dreams might have survived better in waking life. Dreams were rehearsal for danger. Revonsuo later expanded this to social simulation theory—dreams as practice for navigating complex social relationships.

The most recent entry comes from neuroscientist David Eagleman and colleague Don Vaughn in 2021. Their defensive activation theory addresses a peculiarity of brain organization: neural territory is constantly up for grabs. Brain regions that aren't being used can be colonized by neighboring functions. During the long hours of darkness when we sleep, the visual system has nothing to do. Dreams might exist to keep the visual cortex busy, preventing it from being taken over by hearing or touch.

Erik Hoel proposes something different again, drawing on artificial intelligence research. Neural networks that train too specifically on past data develop a problem called overfitting—they become too perfectly adapted to previous examples and fail when encountering new situations. Dreams, with their bizarre combinations and impossible scenarios, might function to prevent overfitting in human brains. They're a source of novel experiences that keep our minds flexible.

Dreams and Religion

Dreams appear prominently in virtually every major religious tradition. This makes sense: if you believe in a realm beyond ordinary perception, dreams seem like an obvious bridge to it.

One theory holds that the very concept of a soul arose from dreaming. The philosopher J. W. Dunne argued that early humans, observing their own dreams, could reach no other conclusion than that something—a soul—left their sleeping bodies and traveled elsewhere. Without that experience, the idea of existence beyond the physical body might never have occurred to anyone.

In Hindu scripture, specifically the Mandukya Upanishad, dreaming is one of three states the soul experiences during life, alongside waking and deep sleep. These ancient Indian texts, written before 300 BCE, present two interpretations of dreams: they might be expressions of inner desires, or they might represent the soul temporarily departing the body.

Jewish tradition treats dreams as part of worldly experience, something to be interpreted and learned from. The Talmud dedicates several pages to dream interpretation, treating it as a legitimate skill. Ancient Hebrews, being monotheistic, believed dreams came from their single God, though they also acknowledged bad dreams from evil spirits. The Hebrew Bible is filled with significant dreams—Joseph interpreting Pharaoh's vision of seven fat cows followed by seven lean ones as a prophecy of abundance followed by famine, the prophet Samuel receiving divine messages while sleeping in the temple.

Christianity inherited these Hebrew traditions. The most famous biblical dream is Jacob's ladder, a vision of a stairway connecting earth to heaven with angels ascending and descending. Many Christians today still believe God can communicate through dreams.

The Mystery Remains

We have accumulated enormous knowledge about dreams over the past century. We know when they occur, what they typically contain, how they vary across cultures and circumstances. We have sophisticated theories about their purpose and increasingly detailed maps of the brain regions involved.

Yet the essential mystery persists. Every night, consciousness takes a strange detour through landscapes of its own creation, and we still don't really understand why or how. The scientific study of dreams, called oneirology, continues to grapple with fundamental questions that would have been recognizable to ancient Babylonian priests or Greek philosophers.

Perhaps this is appropriate. Dreams exist at the intersection of biology and meaning, neuroscience and narrative, the measurable and the ineffable. They are the most private of experiences—no one can enter your dreams—yet also universal. Every human who has ever lived has dreamed.

Tonight, you will close your eyes and become someone slightly different, living through events that never happened in places that don't exist. You probably won't remember most of it. But for a few hours, your brain will generate reality from nothing, telling stories to an audience of one.

What that means, and why it happens, remains one of the great open questions about what it is to be human.