The Real Reason You Dream (Backed by Science)

The 5 Surprising Functions of Dreams

8 min read

1 hour ago

Listen

Every night, regardless of who we are or where we live, we immerse ourselves in a world of subjective experiences as vivid as they are enigmatic…

The world of dreams.

It is one of the universal constants of human experience, represented in every artistic expression and speculated upon since time immemorial. And yet, it remains a mystery. Dreams often seem absurd, fragmented, a random collection of events.

But… what if they aren’t?

That was the question that led me to investigate this mysterious phenomenon.

Modern scientific research, armed with the tools of neuroscience and psychology, is beginning to reveal that this nocturnal theater of the mind has deep, practical, and often surprising functions.

Let’s explore 5 of the most striking and counterintuitive discoveries about the true function of dreams, based on recent studies and classic research that has reshaped our understanding of what happens when we close our eyes.

Dreaming is far more than a nightly spectacle.

Let’s dive deep into this topic…

1. Dreaming is an evolutionary adaptation

Dreaming exists because surviving without dreaming was worse.

From an evolutionary perspective, the brain is a costly and vulnerable organ. It consumes nearly 20% of the body’s energy, even during sleep (Attwell & Laughlin, 2001). During REM sleep, brain activity approaches waking levels (Maquet et al., 1996).

If dreaming were useless, natural selection would have discarded it long ago.

Moreover, dreaming is not exclusive to humans. It has been observed in mammals such as cats (Marrosu et al., 1995). The universality of this phenomenon is a clear evolutionary clue: the dream system is ancient and functional.

From this, a theory emerged…

2. Dreaming to simulate other worlds

The brain dreams “in negative” to anticipate mistakes that could cost a life.

Revonsuo (2000) proposed the Threat Simulation Theory (TST). According to this theory, dreaming emerged as an adaptation to simulate relevant worlds when the external environment is unavailable. In other words, the brain does not shut down — it switches from perceiving the outside world to generating possible scenarios.

Dreaming allows us to recreate alternative versions of what we already know.

And the empirical data are surprisingly consistent.

Analyses show that negative emotions dominate between 60% and 80% of dreams, with aggression present in 45% of dream social interactions (Hall & Van de Castle, 1966; Domhoff, 1996). Moreover, the dreamer is the victim (not the aggressor) in nearly 80% of aggressive episodes, reinforcing the hypothesis of evasive training and danger anticipation.

The most revealing evidence comes from traumatized populations.

In 2003, Valli and his research group observed that Kurdish children exposed to war and violence had more dreams per night, a higher frequency of threats, and greater severity of simulated dangers than non-traumatized children. The dream system was not broken — it was hyperactivated by real signals of constant danger.

Nightmares, therefore, are simulations of unresolved problems.

3. Sleeping to remember and dreaming to forget emotions

Sleep does not erase the past — it separates memory from pain.

One of the most influential theories is Sleep to Remember, Sleep to Forget (SFSF) by Walker and van der Helm (2009). During REM sleep, emotional memories are consolidated while the emotional charge associated with them is reduced.

Neurochemically, during REM sleep norepinephrine drops to its lowest level of the entire circadian cycle (van der Helm et al., 2011). Since this neurotransmitter is directly involved in the stress response, its absence creates an ideal environment to reactivate memories without reactivating suffering.

New discoveries reinforce this idea.

In 2024, Zhang and his research group found that only people who remembered their dreams showed reductions in emotional activity. In other words, those who do not recall their dreams maintain high emotional activity, indicating that dreaming is not passive — it is an active part of emotional processing.

When this system is disrupted, nightmares increase and patterns of incorrect emotional processing emerge (Álvarez et al., 2024).

Dreaming is the brain’s way of fixing memories without reopening the wound.

4. Training for social life

Evolution made us more social, and the brain adapted.

As physical threats became less constant for humans, the brain redirected its simulator toward social conflict. Social Simulation Theory expands on the Threat Simulation Theory discussed earlier.

And new findings support this view.

In 2019, Tuominen and his research group found something crucial: 83% of dreams contain social situations. Moreover, dreams include more characters, more interaction, and more conflict than daily waking life. This aligns with neurological studies: during REM sleep, there is hyperactivity in the amygdala and hippocampus and reduced activity in the prefrontal cortex, making it easier to simulate intense and realistic emotions (Maquet et al., 2005).

Dreaming about arguments, reunions, or rejection is not a coincidence.

Get Mental Garden’s stories in your inbox

Join Medium for free to get updates from this writer.

It is a nightly rehearsal for the complex social life of the waking world.

We make mistakes in dreams so we don’t have to pay for them while awake.

5. Dreaming is not about replaying memories

Dreaming does not exist to better record the past — it exists to prepare the future.

The popular idea that “dreaming about something helps you remember it better” does not fit the data: dreams rarely reproduce an episode literally. In the study by Fosse et al. (2003), 65% of people included some echo of recent experiences, but faithful repetition of a waking event appeared in only about 1–2% of dreams. The rest tended to emerge as loose “fragments.”

And in 2025, a new theory emerged.

The REM Refine & Rescue (RNR) hypothesis suggests that during REM sleep, the brain increases the signal-to-noise ratio, omitting irrelevant details and preserving the essential elements of memories. The result is memory filtering that helps retain what is valuable, adapt, and create solutions (Shuster et al., 2025).

Dreaming is not about remembering more — it’s about understanding better.

So… what are dreams really for?

Dreams don’t do just one thing — and this is what current science has uncovered…

Threat simulation
Emotional regulation
Social training
Creative integration of experiences

What dreams do not do is predict the future, send coded messages, or reveal hidden truths. What they do is keep your mind flexible, emotionally stable, and prepared for the complexity of the world that awaits when you open your eyes.

The question is not, “What does this dream mean?”

The question is: “What was my brain preparing me for?”

Want to learn more? Here are 2 related ideas to go deeper:

✍️ Your turn: Have you noticed more intense dreams during periods of change, stress, or important decisions? Do you have recurring dreams?
💭 Quote of the day: “Are you sure we are awake? It seems to me that we are still asleep, dreaming.” — William Shakespeare, A Midsummer Night’s Dream

🌱 Here I plant ideas. In the newsletter, I make them grow.

Daily insights on self-development, writing, and psychology — straight to your inbox. If you liked this, you’ll love the newsletter. 🌿📩

👉 Join 50.000+ readers: Mental Garden

See you in the next letter, take care! 👋

Referencias 📚

Alvarez, M. M., Balthasar, Y., Verbraecken, J., Claes, L., Van Someren, E., Van Marle, H. J. F., Vandekerckhove, M., & De Picker, L. (2024). Systematic review: REM sleep, dysphoric dreams and nightmares as transdiagnostic features of psychiatric disorders with emotion dysregulation — Clinical implications. Sleep Medicine, 127, 1–15. URL
Attwell, D., & Laughlin, S. B. (2001). An Energy Budget for Signaling in the Grey Matter of the Brain. Journal Of Cerebral Blood Flow & Metabolism, 21(10), 1133–1145. URL
Domhoff, G. (1996). Finding Meaning in Dreams: A Quantitative Approach.
Hall, C. S., & Van de Castle, R. L. (1966). The Content Analysis of Dreams.
Maquet, P., Péters, JM., Aerts, J. et al. Functional neuroanatomy of human rapid-eye-movement sleep and dreaming. Nature 383, 163–166 (1996). URL
Maquet, P., Ruby, P., Maudoux, A., Albouy, G., Sterpenich, V., Dang-Vu, T., Desseilles, M., Boly, M., Perrin, F., Peigneux, P., & Laureys, S. (2005). Human cognition during REM sleep and the activity profile within frontal and parietal cortices: a reappraisal of functional neuroimaging data. Progress In Brain Research, 150, 219–595. URL
Marrosu, F., Portas, C., Mascia, M. S., Casu, M. A., Fà, M., Giagheddu, M., Imperato, A., & Gessa, G. L. (1995). Microdialysis measurement of cortical and hippocampal acetylcholine release during sleep-wake cycle in freely moving cats. Brain Research, 671(2), 329–332. URL
Revonsuo, A. (2000). The reinterpretation of dreams: An evolutionary hypothesis of the function of dreaming. Behavioral And Brain Sciences, 23(6), 877–901. URL
Shuster, A. E., Morehouse, A., McDevitt, E. A., Chen, P., Whitehurst, L. N., Zhang, J., Sattari, N., Uzoigwe, T., Ekhlasi, A., Cai, D., Simon, K., Niethard, N., & Mednick, S. C. (2025). REM refines and rescues memory representations: a new theory. SLEEP Advances, 6(1). URL
Tuominen, J., Stenberg, T., Revonsuo, A., & Valli, K. (2019). Social contents in dreams: An empirical test of the Social Simulation Theory. Consciousness And Cognition, 69, 133–145. URL
Valli, K., Revonsuo, A., Pälkäs, O., Ismail, K. H., Ali, K. J., & Punamäki, R. (2003). The threat simulation theory of the evolutionary function of dreaming: Evidence from dreams of traumatized children. Consciousness And Cognition, 14(1), 188–218. URL
Van Der Helm, E., Gujar, N., Nishida, M., & Walker, M. P. (2011). Sleep-Dependent Facilitation of Episodic Memory Details. PLoS ONE, 6(11), e27421. URL
Walker, M. P., & Van Der Helm, E. (2009). Overnight therapy? The role of sleep in emotional brain processing. Psychological Bulletin, 135(5), 731–748. URL
Zhang, J., Pena, A., Delano, N., Sattari, N., Shuster, A. E., Baker, F. C., Simon, K., & Mednick, S. C. (2024). Evidence of an active role of dreaming in emotional memory processing shows that we dream to forget. Scientific Reports, 14(1), 8722. URL