The brain is not a computer

There are moments when an idea feels like something you always knew, but couldn't yet articulate. I had one such moment last week, when I read a book review in Nature. The neuroscientist Romain Brette has written a book that I can scarcely summarise without doing it an injustice: The Brain, In Theory (Princeton University Press, 2026). But the essence can be articulated.

The brain is not a computer.

Not 'in certain ways not' or 'not in a philosophical sense'. Brette's argument is fundamental: the brain is not programmable, neural activity is not code, and the brain does not process information in the meaning that engineers and computer scientists give to that word. For three decades, neuroscience has treated a metaphor as a fact. Brette calls this 'epistemic phlogiston', after the fictitious element once invented to explain fire. The word seemed to answer the question, whilst it only reformulated the question. Convenient. Wrong.

This is about AI. Why should you be interested?

Because we live at a time when everyone is forming an opinion about what AI can and cannot do. Some fear it will make us redundant. Others believe it will solve our problems. Both start from the same silent assumption: that the human brain is a computer, just a biological one. If that assumption is correct, it's merely a matter of time before machines do it better than we do. More computing power, fewer errors, no sleep deprivation.

If that assumption is incorrect, the entire comparison changes.

What you feel when you see a chair

Brette uses an example that won't let me go. Imagine you're sitting in a room and you see a chair. What do you do? You don't classify the chair as an object in the category 'furniture, subtype seating'. You already feel your own body sitting. You anticipate the movement, the backrest, the weight on your spine. You know what the chair means for you in the most literal, physical sense. Not because you calculate it. But because you have a body, in a world full of chairs.

An AI sees pixels. Compares them with millions of other pictures of chairs. Classifies correctly. Reproduction: 99.9%.

But it never sits.

That is the essence of what Brette says. Cognition is not computation; it is knowing through doing. He introduces anticipation as the core concept of cognition and life: our brain does not calculate what is there, it prepares the body for what is coming. The chair you see already evokes the movement you will make. That is not information processing. That is something fundamentally different.

Our brain does not consist of fixed rules or commands. It is, in his own words, 'the collective behaviour of a colony of living entities': not a distributed computer, but a self-organising system inextricably connected to a body that lives, moves and perishes. Neurones respond to context, to history, to the state of the system as a whole.

The engineer trying to understand a brain, Brette says, is like someone trying to understand love by studying the accounts. The figures add up. The point missed.

What I know from personal experience

On 15 November 2024 I fell from my e-bike in the Noorderplantsoen in Groningen. My heart raced, 260 beats per minute, and I was gone for a moment. The diagnosis after admission to the UMCG: subarachnoid haemorrhage, skull base fracture, blood in the lateral ventricle. Acquired brain injury.

What followed teaches you more about how the brain works than most books ever will.

A computer that becomes damaged becomes proportionally damaged. Less RAM means less capacity everywhere. But my brain did something different. The cognitive screening revealed that my information processing was slower, my divided attention impaired and my error monitoring fleeting. But my prefrontal cortex, planning, abstract thinking, reflection, worked undiminished. Two separate systems. Two separate functions. The damage was in the limbic system: I could think clearly, but motivation felt sluggish.

What I later learnt to distinguish: the damage affected the meaning-layer, not the making-layer. Why am I doing this? That was the question that gave no answer. But just making something properly, that simply worked. Two separate circuits. That doesn't exist in a computer.

And the most remarkable thing was the recovery. That wasn't repair like replacing a broken module. It was living. Movement as medicine. Morning light as anchor. One thing at a time, not because I wanted to, but because the system demanded it. The method was called Stop-Think-Do: pause before each action, think, then only execute. Sounds simple. It isn't, when you're used to doing everything quickly.

That word, quickly, has since disappeared from my vocabulary. I no longer do something quickly. That sounds like loss. It feels like gain. Fast thinking has diminished. I never just give an answer any more. I work much more precisely. The brain reorganised itself not by being repaired, but by living differently, in relation to a body that kept moving, a day that kept beginning, a world that kept offering.

Precisely what Brette describes: a living system, not a programmable machine. I had this proof in my own skull. I only saw it properly when I read this article in Nature.

AI doesn't take over what you are

This doesn't mean that AI isn't powerful. On the contrary. AI is astonishingly good at what computers naturally do: recognising patterns, generating text, writing code, producing images. I use it every day. It makes my work faster, sharper, further-reaching.

But the fear that AI will 'take us over'? That rests on the idea that what makes us human ultimately comes down to the capacity for calculation. If Brette is right, that's misplaced. What distinguishes us isn't that we associate faster or reason better. It's that we have a body. A history. A specific chair in a specific room, at a specific moment, with everything we bring to that moment.

A brand is no different. A strong brand is not an algorithm, not a positioning document, not a consistent house style. It is the residue of decisions that a person made based on what they valued, feared, learnt and survived. It lies in the voice with which an entrepreneur speaks about their clients. In what they refuse to do when the pressure increases. In the choices they made before they knew they were choices. All these things together form something that cannot be replicated, not because it's too complex, but because it was never engineered. It grew, as brains grow, in relation to a world it physically inhabited.

Yes, but an aeroplane isn't a bird either

Here comes the sharpest objection to everything I've written so far, and I don't want to brush it aside. Suppose Brette is completely right. Suppose the brain truly isn't a computer. It still doesn't follow that AI cannot take over your work. After all, an aeroplane doesn't fly like a bird either. It has no feathers, it doesn't flap, it doesn't know what wind is. And yet it has taken over the journey. A machine doesn't need to be a brain to do what a brain did.

That objection is correct. And precisely because of that, it shows where the real boundary lies.

There is a difference between taking over a task and being what someone is. The aeroplane took over travel, bridging a distance from A to B. That was a task. No one afterwards confuses the aeroplane with the bird, and no one ever asked the aeroplane to brood, to sing or to build a nest. AI takes over tasks, more and faster than I thought possible two years ago. Text, code, image, analysis: they are tasks, and machines do them.

But a brand is not a task. A voice is not a task. The choice to let a client go when the pressure increases is not a task. These are things that have grown from a body with a history, and you cannot detach them from that without them ceasing to be what they were. The aeroplane took over flying and left the bird alone. AI takes over calculating and leaves behind what was never computational work.

That is not replaceable. Not because the technology cannot yet do it. But because technology was never the right sort of thing to take it over.

Good news, then

Over the past two years I've written more about AI than about almost any other subject. My central conviction was always the same: AI is the greatest development of this moment, and it doesn't make people redundant. I could substantiate that well from brand, communication, strategy. But somewhere there always hung a feeling that I was saying more than I could prove.

Now a neuroscientist from Princeton has given me the foundation. Not to prove me right, but to sharpen the distinction. The brain is not a machine you can optimise or replicate. It is a living system that organises itself in relation to a world it physically inhabits. And what grows from that, a brand, a voice, a way of seeing, is not a task waiting to be taken over.

AI can do a great deal. But it inhabits nowhere.

Sources

Based on: Àlex Gómez-Marín, 'How to breathe life back into brain theory', Nature (May 2026). Review of: Romain Brette, The Brain, In Theory, Princeton University Press, 2026.