Dreams emerge across different stages of sleep and may reflect memory and emotional processing, but scientists have not identified a single biological purpose that explains why we dream.
THE UNIVERSAL RECORD
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Brad Socha | August 13, 2026 | 10:46 PM EST
A dream can feel as convincing as waking life, combining people, places, emotions and events into experiences that may be vivid, fragmented or bizarre. Neuroscience has established that dreaming is closely tied to changing patterns of brain activity during sleep, particularly rapid eye movement, or REM, sleep. What remains unsettled is the larger question: why does the brain create these experiences at all?
Dreaming is not confined entirely to REM sleep. People can report dreams after being awakened from non-REM stages as well, although REM dreams are often especially vivid and emotionally rich. During a typical night, the brain repeatedly cycles through non-REM and REM sleep, usually completing four to six cycles. REM periods generally become longer later in the night.
The fact that dreaming accompanies measurable changes in brain activity has given researchers clues about how dreams are produced. It has not, however, produced scientific agreement on whether dreaming itself serves one essential function.
What Happens in the Brain During a Dream
REM stands for rapid eye movement, referring to the characteristic eye movements seen beneath closed eyelids during this stage. Brain activity becomes relatively active, breathing can become more irregular, and heart rate and blood pressure move closer to waking levels. At the same time, most voluntary skeletal muscles are temporarily inhibited, a state known as muscle atonia that normally prevents people from physically acting out their dreams.
Much of the research into dreaming focuses on memory.
Sleep clearly contributes to memory consolidation, the biological processes through which newly acquired information becomes more stable, but the relationship between dreaming itself and memory remains less certain. A 2024 review in Consciousness and Cognition found that studies examining whether dreaming about learned material predicts better memory have produced mixed results, partly because dreams are difficult to measure objectively and research methods vary substantially.
That distinction is important. Evidence that sleep helps memory does not automatically prove that the subjective experience of dreaming is necessary for memory consolidation.
Research also suggests that emotional experiences and REM sleep are connected. Studies have implicated REM sleep in processing emotional memories, including fear-related information, and several theories propose that dreaming may be involved in integrating emotionally significant experiences. Yet researchers are still working to determine whether dreams actively perform this function or simply accompany underlying brain processes occurring during sleep.
This may help explain why fragments of waking life frequently appear in dreams without being reproduced exactly. People, locations, concerns and memories can be recombined into narratives that bear only a loose relationship to the events that inspired them.
Nightmares, Lucid Dreams and What Remains Unknown
Not every dream is pleasant.
Nightmares are disturbing dreams that can produce strong emotions and awaken the sleeper with a clear recollection of what occurred. Occasional nightmares are common, while recurrent nightmares can become clinically significant when they repeatedly disturb sleep or cause substantial daytime distress. They can also occur alongside conditions such as post-traumatic stress disorder.
Scientists have proposed that dreams could contribute to emotional regulation by allowing the brain to process emotionally important material in altered contexts. Some research supports an association between dreaming and emotional adaptation, but this remains an area of active investigation rather than a settled explanation for why all dreaming occurs.
An especially intriguing form is lucid dreaming, in which a person becomes aware that they are dreaming while the dream continues. Lucid dreaming has been physiologically documented for decades and occurs predominantly in REM sleep, although scientists still do not fully understand the neural mechanisms that allow waking-like self-awareness to emerge within a dream.
Being lucid also does not necessarily mean having complete control over the dream. Some people can deliberately influence what happens, while others simply recognize that the experience is a dream.
Researchers have investigated lucid-dreaming techniques as possible treatments for recurrent nightmares. A 2023 systematic review found encouraging evidence that lucid-dreaming therapy may reduce nightmare frequency, but the available studies were limited and the authors concluded that larger, more rigorous trials are needed. The American Academy of Sleep Medicine has listed lucid-dreaming therapy among approaches that may be used for nightmare disorder, while recommending imagery rehearsal therapy more strongly.
Dream research ultimately faces an unusual scientific problem: researchers can measure brain waves, eye movements, muscle activity and other physiological signals while someone sleeps, but the dream itself remains a subjective experience that usually must be described after awakening.
That makes simple explanations difficult to prove.
Dreams may reflect several processes occurring at once rather than performing one universal task. Memory consolidation, emotional processing, recent experiences and spontaneous patterns of brain activity may all contribute to what people experience while asleep. Current evidence supports connections between these processes and dreaming, but none has established a single purpose that accounts for every dream.
Science therefore understands considerably more about when and how the brain dreams than why it dreams. The answer may eventually turn out not to be one function at all, but a consequence of several essential processes continuing while the sleeping brain remains remarkably active.
Sources:
National Institute of Neurological Disorders and Stroke — Brain Basics: Understanding Sleep
https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep
National Heart, Lung, and Blood Institute — How Sleep Works: Sleep Phases and Stages
https://www.nhlbi.nih.gov/health/sleep/stages-of-sleep
National Heart, Lung, and Blood Institute — Why Is Sleep Important?
https://www.nhlbi.nih.gov/health/sleep/why-sleep-important
Consciousness and Cognition / PubMed — Enhancing and Advancing the Understanding and Study of Dreaming and Memory Consolidation
https://pubmed.ncbi.nlm.nih.gov/38941924/
Neurobiology of Learning and Memory / PubMed — Emotional Memory Processing During REM Sleep
https://pubmed.ncbi.nlm.nih.gov/36639913/
Frontiers in Psychology / PubMed Central — The Functional Role of Dreaming in Emotional Processes
https://pmc.ncbi.nlm.nih.gov/articles/PMC6428732/
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About the Author
Brad Socha is the founder of The Universal Record, focused on sourced, factual global reporting. Coverage includes international news, geopolitics, technology, and major developments.