Every night we lay down to rest, we spend about two hours traveling through seemingly real experiences as dreams bubble up from our subconscious during various phases of sleep. 

The origin, meaning, and mechanisms behind dreams have spurred speculation since the dawn of recorded history. Despite the ubiquity of the experience—and the advent of modern medical technology—where dreams come from, and what their purpose is, remains largely unanswered.

Meaning & Purpose

For millennia, dreams have been a prime example of pareidolia—humans' impulse to find meaning in ambiguous images and visual patterns. 

Early history is filled with examples of vivid dreams interpreted as prophecy, divine revelation, or a bridge between the living and the dead. Ancient Babylonians established and left instructions for their complex system of dream reading (see overview).

Sigmund Freud brought dream theory into the modern era at the beginning of the 20th century, arguing dreams were often the fulfillment of unconscious wishes (explore his seminal work on dreams).

Another pioneer in the field, Freud's close colleague Carl Jung, took a different approach. Jung theorized that dream symbolism was pulled from a collective unconscious, reflecting a set of universal instincts and archetypes. 

Beyond their meaning, psychologists have variously suggested the purpose of dreams is to process difficult emotions, consolidate memories, mentally rehearse real-life experiences, or are just a byproduct of the complex brain.   

Inside the Brain

Sleep generally occurs in two types: non-REM and REM (rapid eye movement). Dreaming happens across all types of sleep; however, the majority of dream states unfold during REM phases when the body is paralyzed, with brain waves closely resembling those during waking periods. 

Certain brain regions fire away during REM. In particular, the thalamus (which relays sensory information) sends signals to the cortex (which processes information from memory) encoding images, sounds, and more, mimicking waking states (see overview).

Separately, the hippocampus—the brain's memory center—plays a central role in dream construction. Half of all dreams draw from specific real-life experiences, according to one study, and patients with a damaged hippocampus have been shown to experience less detailed dreams. 

Lucid dreaming, where subjects are aware they're dreaming and can exert control over their actions, is of particular interest. Studies suggest at least eight different brain circuits combine to produce (see Fig. 1) the unique experience, including those shown to play a role in self-awareness and planning. 

Roughly one in 250 people reports having never dreamed at all, though researchers believe such sleepers functionally dream but are prevented from remembering them by some unknown underlying cause.

Dive Deeper

Relevant articles, podcasts, videos, and more from around the internet - curated and summarized by our team

Photo of a winged child sleeping on clouds.
Open link on quantamagazine.org

Scientists are still trying to figure that out. It's difficult to measure and study dreams as scientists can only study the private, subjective experiences secondhand, a complication also known to pain researchers. What scientists do know is that dreams are creations of the brain during sleep that can involve time, space, emotions, and social interactions and range in experience from immersive to abstract.

National Geographic

Do animals dream?

Photo of a red panda sleeping in a tree.
Open link on nationalgeographic.com

Sleeping cats that had part of their pons—part of the brainstem seemingly involved in REM sleep and sleep paralysis—removed engaged in behaviors as if they were awake. Studies on sleeping rats, fish, and finches show their brains fired as if performing actions from waking life. Spiders and insects also have REM-like sleep. Whether these findings indicate animals dream depends on one's definition of dreaming.

University of Pennsylvania Museum of Archaeology and Anthropology

Interpret your dream like an ancient Babylonian

Open link on penn.museum

Ancient Babylonia was a hub for oracular studies. Dreams were seen as nightly dispatches from lower world or chthonic deities, and practices including astrology, omen reading, and liver divination attained wide-reaching influence. Few surviving records of oneiromancy—interpreting dreams as revelations of future events—have been found. This article details an ages-old Babylonian tablet, in "almost perfect" condition, filled with nearly 90 omens and their interpretations.

Open link on knowablemagazine.org

The theory of where dreams originate began shifting from ancient mystical explanations to modern scientific ones at the beginning of the 20th century with the work of Austrian psychologist Sigmund Freud. The invention of the electroencephalogram in the 1920s gave scientists the ability to track electrical activity in the brain, solidifying some of the field's softer science into observable data and giving rise to sleep labs.

Photo of person holding a bloody knife looking through a glass door.
Open link on youtube.com

Nightmare comes from the terms night and mare, an Old English word for evil, suffocating spirits. Shifting into today's understanding of the term, nightmares are parasomnias, meaning they are undesirable events experienced during sleep, and may stem from building tensions in one's unconscious. Bad dreams and nightmares differ in that the latter forces one awake, usually with unpleasant emotions and a rapid heart rate.

Photo of out-of-focus person standing near a curtain-covered window.
Open link on vox.com

When the body falls into a deep enough phase of sleep, it paralyzes certain parts of itself so the brain can't force it to physically act out dreams. More than 20% of people will experience a short circuit of this system, resulting in sleep paralysis. This well-known but little-understood phenomenon happens when the brain awakens early and typically results in haunting hallucinations and reports of supernatural terrors.

Explore all Dreams

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