What if dreaming is the whole point of sleep?

Original Article ↗ Hacker News Discussion ↗

Speculation that dreaming is the primary purpose of sleep prompts debate over what sleep is really for: emotional processing, memory consolidation, “retraining” neural pathways, or simply keeping the body and brain alive. Commenters point to evidence for multiple overlapping functions, from glymphatic “cleaning” of the brain and metabolic reset to REM-related learning and psychological insight, and argue that calling dreams the “whole point” ignores the lethality of severe sleep deprivation. The thread also touches on whether animals and AI might “dream,” how brain architecture differs from engineered systems, and how medications or lifestyle factors alter the vividness and perceived value of dreams.

Link and overall reaction

  • Multiple commenters note the original URL had a typo; fixed versions are shared.
  • The article is seen as interesting but some find the “dreaming is the whole point” framing overstated or “silly.”

Functions of sleep vs. functions of dreaming

  • Many argue sleep has multiple purposes: physical recovery, metabolic cleanup, and cognitive processing.
  • Glymphatic “flushing” of waste during sleep is repeatedly cited as a core, possibly life-or-death, function.
  • Several see dreaming as one function among many, not the main one. Some report feeling well-rested after sleep or naps with no remembered dreams.
  • Others propose that REM/dreaming reprocesses experiences, changes “weights” in neural circuitry, and supports learning (e.g., improving at sports after practice).

Neural mechanisms and AI analogies

  • One line of discussion likens dreams to noise injection or “reweighting” in neural networks; others rebut that brain plasticity involves dendrite growth, myelination, and inhibitory neurons rather than simple down-weighting.
  • Multiple comments compare dreaming to a flight simulator or disk defragmentation.
  • Some speculate that if dreams serve training/regularization purposes in humans, analogous “dreaming” phases might help AI/LLMs.

Evolutionary and behavioral perspectives

  • Explanations for why cleanup and dreaming require sleep include: reduced sensory input, phase separation of functions, energy budgeting, and accumulated evolutionary dependencies.
  • Some suggest sleep also evolved to keep organisms still and quiet during predator-active hours.
  • There’s debate over whether we experience dreams as fully “real,” and whether evolution has effectively given us “two lives” (waking and dreaming).

Animals, consciousness, and evidence

  • Observations of twitching, running, and vocalizing dogs/cats lead many to infer animal dreaming.
  • Others counter that without verbal reports, dreaming in non-humans isn’t provable; supporters reply that, by the same logic, we can’t conclusively prove other humans dream either (philosophical-zombie argument).
  • REM-like states in other mammals and birds are mentioned as suggestive but not definitive.

Psychological/therapeutic role of dreams

  • A psychotherapy perspective views dreams as “multiplayer”: the dreamer plus an interpreter.
  • Reported patterns: dreamers rarely notice their own behavior, which often exposes unconscious interpersonal anxieties more clearly than waking symptoms.
  • Lucid dreaming is described as emotionally and cognitively exhausting but potentially useful for self-reflection; people often need a second REM phase afterward.

Insomnia, deprivation, and harm

  • Severe insomnia experiences include hallucinations and “breaking down,” reinforcing that sleep itself is medically critical.
  • Historical and clinical examples (e.g., extreme deprivation in interrogations, fatal insomnia syndromes, rodent studies) are cited to argue that prolonged sleeplessness can be lethal, though causality details are debated.
  • Some see dreams as possibly therapeutic, possibly harmful, but usually forgotten; core survival value is attributed to sleep, not dreaming.

Brain vs. computers and imagination

  • Commenters note how poorly we still understand the brain despite long familiarity, contrasting it with engineered, modular computers.
  • Energy comparisons: the human body ~100 W, with a portion for the brain; laptops generating language at ~30 W are contrasted with human efficiency and evolutionary “training.”
  • There’s an extended subthread on visual imagination: some claim “retina-like” subjective resolution; others say mental imagery is lower resolution and just-in-time detailed. The spectrum from strong visualization to aphantasia is discussed.

Dream content and modifiers

  • One hypothesis: the less one engages with fantasy/media, the more mundane dreams become; exposure to fantasy may enable more bizarre dreams.
  • Various subjective reports: pets dreaming vividly, déjà vu, and drug/supplement effects (trazodone dampening dreams for some; lion’s mane mushroom claimed to intensify them).