Dreams are weird.


For one, they’re interesting in general, but very boring in isolation. People often like to know more about dreams and what they mean, or represent, or why they happen. By contrast, hardly anybody likes to hear about someone’s specific dream.

But the reason people are compelled to tell you about their dream (when they can remember them, which isn’t guaranteed), is typically because they involved fantastical, unlikely occurrences. Utterly impossible events happen, then immediately flow into completely different ones, with no obvious rhyme or reason. Contexts, behaviours, individuals, they all shift around randomly during our dreams, with no care for coherent narrative or the laws of physics. It’s all very weird.

Except, rarely does it feel weird while it’s happening. We can be dreaming about floating upside down in a cavern of milk, sat alongside someone who is both our mother and co-worker at the same time, and our dreaming self will still think “Yep, this is all to be expected. Typical Tuesday occurrence”.

Why is this? Why would our sleeping brain be so blasé about deeply unusual reality-bending experiences?

A big part of this is down to the reason we dream in the first place. A growing body of research strongly suggests that dreaming is a vital part of memory consolidation. Our brains don’t just create all of the memories we accumulate while we’re awake and leave them sat there purposelessly, like most of the photos on the typical smartphone.

No, our newly acquired memories need to be effectively integrated into the brain’s stores and networks of existing memories that are the basis of our identify, our sense of self, our very minds, and more. This is what memory consolidation is, and a lot of it takes place during our dreams.

Again, this makes a lot of sense, because the time when we’re asleep is the time when new memories aren’t continuously being created and added to the to-be-consolidated pile. It’s like how people working on a road make sure it’s closed first, because trying to do their job while cars are still using it would be considerably more difficult.

It’s also important to note how we believe memories are stored in the human brain. Biological memories aren’t separate, distinct, standalone files of complex information, like the aforementioned photo images in a smartphone. No, it seems that our memories are made up of discrete elements, linked up in unique, complex ways.

For instance, if you’re in a long-term relationship, your partner's face will be one of the most familiar things you encounter in your waking life. But if your brain was to create a whole new memory of your partner’s face every time you see them, soon you’d have tens of thousands of memories, all for the exact same thing. This is in no way efficient, particularly for an organ as demanding as the brain.

Instead, it’s more that you have one established memory of your partner's face, and when new memories are formed that involve them, those memories are linked to the stored representation of their face.

Elements of memory can represent anything we experience. Sights, sounds, emotions, colours, people, and more. Combining and connecting these elements in useful ways is what memory consolidation, or dreaming, is for. As far as we know.

But when these memory elements are being worked on while we’re asleep, they’re also being ‘activated’, like how you need to run power through an electrical circuit to know whether it works. And when a memory is activated, we re-experience it.

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But while conscious experiences are consistent with the laws of nature, dreaming experiences are not beholden to such things. Say, if you are feeling anxious about an upcoming work meeting, then you’ll have a load of new memories with an element of anxiety. To better incorporate this new anxiety element, your dreaming brain will link it to other memories that include an element of anxiety.

Say you remember being anxious before singing in public or doing scuba diving for the first time. Your dreaming brain will connect your new anxiety to these existing memories. The end result could be that you end up dreaming about singing underwater.

This is an impossible act. But your dreaming brain doesn’t care.

Ultimately, everything that happens in a dream is derived from bits of memory, temporarily bound together in complex, baffling ways that your brain imposes a sense of ‘self’ onto, in order to better process things in useful ways.

What this means is, no matter what baffling and impossible things occur in our dreams, they’re always made of things that our brain is already familiar with. Because they’re memories.

It’s as if you came home one day to find your partner has rearranged all your furniture. You might be surprised at the new configuration, but you wouldn’t think “What’s all this new furniture?” Because you’d recognise it.

Just like our dreaming brain does with our memories. They may be presented in whacky, implausible ways, but the sense of ‘this is all familiar’ endures. Because, as far as your brain is concerned, everything is familiar.

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Dean is a neuroscientist, author, blogger, occasional comedian and all-round ‘science guy’. He is the author of the the popular Guardian Science blog ‘Brain Flapping’ (now ‘Brain Yapping’ on the Cosmic Shambles Network with accompanying podcast), the bestselling books The Idiot Brain and The Happy Brain, and his first book aimed at teens, Why Your Parents Are Driving You Up the Wall and What To Do About It.