How to think outside your brain

Your brain is brilliant at many things. Storage isn’t one of them.

We were raised to treat memory like a filing cabinet. Cram for exams, rehearse grocery lists, memorise phone numbers because Nokia 3310s didn’t sync to iCloud. The message was clear: if you can’t store it upstairs, you’re not trying hard enough.

Spoiler alert: brains aren’t hard drives. They’re processors. They don’t want to hoard information; they want to remix it.

Memory is an unreliable narrator

Every time you remember something, your brain rewrites it. Memory isn’t retrieval—it’s reconstruction. Your neurons grab fragments, sprinkle them with today’s emotions, splice in whatever you just watched on Netflix, and hand you “memory.v47”. No wonder eyewitnesses disagree and siblings argue about childhood stories. The brain isn’t lying; it’s crafting a plausible narrative from incomplete footage.

That’s charming for nostalgia, disastrous for knowledge work. If your workflow depends on perfect recall, you’re building on quicksand.

Working memory is a tiny desk

Even if your brain stored memories perfectly, working memory would still bottleneck you. Most studies pin our mental juggling limit at roughly seven items. Try to hold more and everything splats onto the mental floor.

Complex thinking demands more than seven thoughts: arguments, counterarguments, quotes, data points, your own take, the structure of the piece you’re writing, the hook you want to land. That’s already eight balls in the air.

Sönke Ahrens summed it up neatly: “We need a reliable and simple external structure to think in that compensates for the limitations of our brains.”

Externalise thought, not just storage

The biggest shift in my practice came when I stopped thinking in my head. Not just storing information externally—actually thinking externally.

When I’m wrestling with a messy idea, I open a note (or dictate into an AI) and dump every half-baked thought. Short sentences. Question marks. Contradictions. The point is to get the fog out of my skull and onto the screen where I can see it.

This isn’t diary writing. It’s conversational debugging. I treat the page like a junior colleague: “Explain this back to me.” Half the time the page just stares blankly, which tells me I don’t have clarity yet.

Ahrens nails the payoff: “The most important advantage of writing is that it helps us confront ourselves when we do not understand something as well as we would like to believe.”

Brains love connections, not cold storage

Brains remember through association. Smells trigger childhood, songs unlock entire summers, one joke resurfaces another. This is the secret sauce of zettelkasten: treat notes as connection points, not trophies.

When I write a permanent note (see three note types that transform thinking), I’m not immortalising the information. I’m planting a hook my future self can grab. My brain only needs to remember “I have something on Luhmann and laziness”; the note contains the specifics.

That division of labour means my brain stays in pattern-recognition mode while my notes handle the exact wording, references, and links.

Forget strategically to remember better

Paradoxically, the more I outsource to notes, the more I remember. Not verbatim facts, but shapes: arguments, narratives, analogies. When I need detail, I look it up. My mental energy stays focused on synthesis.

Writing things down deepens understanding because translation forces processing. You can’t explain something you don’t grasp. Cognitive scientists call this the generation effect. I call it “future Jenxi will thank you.”

This is also why I let ideas marinate. By the time I revisit a note, I’ve forgotten the exact phrasing. The distance lets me spot patterns I missed. It’s the same reason photographers let raws sit before editing: detachment sharpens judgement.

Build a dialogue with your notes

Once thinking happens outside your head, your notes become conversation partners. One note pointing to another sparks an insight you didn’t plan. A question from July collides with a quote from October and suddenly there’s a newsletter draft staring back at you.

Ahrens again: “The slip-box is designed to present you with ideas you have already forgotten, allowing your brain to focus on thinking instead of remembering.” When your notes surprise you, that’s when you know you’re thinking outside your brain.

Practical ways to think externally

Want to try this today? A quick loop:

Spot a sticky idea in something you’re reading.
Open a fresh note and brain-dump what you think about it. No polishing.
Extract one permanent note: a clear statement, why it matters, links to related notes, and a question that keeps the conversation alive.

Rinse repeat. Before long you’ve built a lattice of externalised thoughts that talk to each other. That lattice is your extended working memory—far bigger than seven items.

Standing on an extended brain

This approach compounds. Every externalised thought becomes available to future you. Every connection makes subsequent connections easier. Your creative system snowballs not because your brain grew more storage, but because you built a trustworthy, searchable, remixable extension.

Or as Ahrens writes, “To have an undistracted brain to think with and a reliable collection of notes to think in is pretty much all we need.”

Let your brain be the processor. Let your notes be the hard drive. Together they form a cyberbrain that actually plays to your strengths.

Next in this series: Learn by reading—how to transform passive consumption into active understanding, and why highlighting might be sabotaging your comprehension more than you realise.