Why do we forget our dreams?

This post is also available in Dutch.

You probably know the feeling: you wake from a deep sleep and vaguely remember something about this dream you had. A few moments later the dream is gone.

Does everybody dream?
An average human spends about a third of his/her life sleeping. In all these sleeping hours, many dreams pass. Dreams can take you to another world, where you can fly with giant giraffes. Or they can take you to an event that happened the day before: you relive an important presentation, only this time you are presenting in your birthday suit. Of all these dreams you probably remember just a few. Some people remember their dreams relatively often, others feel like they never dream at all. Research has shown that all people dream, but the ones who claim they don’t are just the ones that don’t remember. In general, most dreams you have in your life are forgotten. This common phenomenon is called dream amnesia.

Dreams to remember or to forget
There has been quite some discussion about why dream amnesia might exist. Functionally, it makes sense for us to forget our dreams. Dreams are not real; they are not made of experiences from which we should remember to learn. What is peculiar, however, is that our dreams often contain bizarre and strong emotional content which we would definitely remember if we were awake. Moreover, we usually are not aware of the fact that we’re dreaming. If this is the case, and we experience dreams as a real event, why wouldn’t we remember them? Put differently: Why do we forget many of our dreams?

Dreams as reality-simulators
Unfortunately, there is not just one answer to this question. Dream researcher Antti Revonsuo approaches it from an evolutionary perspective. According to his theory, dreams are meant to simulate reality. This way, you can practice handling certain daily-life situations and best prepare for different challenges. While dreaming, or simulating reality, your brain is already practicing. For this reason, the dream itself need not be stored in memory. This is further clarified by distinguishing between declarative (explicit) and procedural (implicit) memory.

Practicing in your dreams
Declarative memory stands for memories of facts and events, or ‘knowing what’. These are memories you can consciously summon. Your procedural memory, though, has to do with learned skills, or ‘knowing how’. These are, in fact, unconscious memories of actions or tasks you mastered, like riding a bicycle (Do you want to know more about the memory? Take a look at one of our other blogs on this topic). Declarative memory seems to be limited during dreaming, as often no explicit memory of the dream is stored. This does not mean your procedural memory is also failing. The suggestion of dreams functioning as a simulation of reality can be considered procedural learning. The skills could then be trained without an explicit memory of the training event (i.e. the dream).

It would be quite disturbing if all our dreams of flying giraffes and scary presentations would stick to our memory. Your brain is constantly working to carefully select information so that you can adequately respond to future events. Information that is for some reason not considered relevant is not going to be stored. So in that sense, forgetting is actually a good thing.

This blog is written by a guest blogger, edited by Mahur & Felix, translated by Rowena and edited by Christienne.

This blog was written by Kyrah Wilmink, researcher at the Donders Institute. Kyrah is doing an internship at the Memory Dynamics lab and investigates how our memory works, mostly by looking at neuronal circuits in the mouse hippocampus.

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