Your Brain Is About to Need a Gym.

I tried to remember my mother's phone number last week.

A number I've dialed maybe four hundred times over the last decade. I stood in the kitchen, looked at my phone, and reached for her name like I always do.

Then I stopped, and tried to recall the digits cold.

I couldn't.

Fine, you'll say. Nobody memorizes numbers anymore. The phone does it. That's the deal.

Sure. But it wasn't the number that bothered me. It was what happened the next morning.

I opened my laptop to draft a two-line logistics email. The kind of thing I'd have typed in ninety seconds last year. I went to Claude before my fingers hit the keyboard. Not to write something hard. To write something easy I just didn't want to think about.

That's when it landed.

I'm getting brain-lazy. And I work on AI for a living.

If I'm getting lazy, so are you.

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There’s no free lunch in the universe, only transformation.

AI productivity isn’t free or cheap. The real payment is our cognitive fitness.

(There’s always a payment. Make sure you’re OK with it.)

Why?

AI doesn't just save you cognitive effort. It builds the muscle that resists cognitive effort. Every offload trains your brain to expect the offload next time. Next time you face the blank page, your brain doesn't reach for the pen. It reaches for the prompt box. Then it reaches for the prompt box for the email after that. Then for the half-decision you used to make in your head while making coffee.

Cars did this to our legs.

AI is doing it to our brains.

Nobody has built the gym yet.

What Cars Did to Our Bodies

In 1900, the average American walked five to ten miles a day. Not for exercise. To live. Walk to the train, walk to the shop, walk to the office, walk home. The body got its workout because the world demanded one.

By 1970, that number had collapsed. We built cars. We built suburbs. We built drive-throughs. The world stopped demanding motion. Productivity exploded. Convenience exploded. The cost didn't show up in spreadsheets, so for a long time nobody noticed it.

The cost showed up in our bodies.

By 2020, obesity was the leading preventable cause of death globally, costing over $1 trillion a year in healthcare and lost productivity. By 2030, the World Health Organization projects that number to roughly double. None of those numbers existed as a category in 1950.

Meanwhile, a second industry quietly built itself to undo what the first one did. The global health-and-fitness market is now around $100 billion. Peloton, ClassPass, Equinox, Strava, every yoga studio, every protein powder, every wearable. None of it existed when our great-grandparents were getting their daily activity from simply being alive in the world.

The pattern is brutally simple. A tool removes a daily demand. The capacity built by that demand atrophies. A new industry emerges to artificially recreate the demand we lost.

AI just removed the daily demand for thinking.

What AI Is Doing to Our Brains

I want to be careful here. I am not making the lazy "AI is making us stupid" argument. That's the kind of take that gets you a viral post and zero new ideas.

What I am saying is more specific.

A 2025 study from Microsoft Research and Carnegie Mellon followed knowledge workers using generative AI tools. The headline finding: the more workers trusted the AI, the less critical thinking they exhibited. The researchers gave it a clean name. Cognitive offloading. You stop maintaining the mental scaffolding because the system maintains it for you. Until the system gets it wrong. And by then, the scaffolding is gone.

This is the same loop I wrote about in Letter 76 ("The Only Skill That Matters") and Letter 85 ("We Stopped Making Seniors"). I keep coming back to it because the evidence keeps stacking. Verification atrophy. Apprenticeship collapse. Now this: the silent, unflashy, generation-wide weakening of the thing that turned us into a knowledge economy in the first place.

The mechanism is uncomfortable, so it doesn't trend.

Most of you reading this offload between thirty and seventy percent of your daily thinking to AI right now. Email drafts. Document summaries. Decisions you "pressure test" with a chatbot before committing. The first draft of every memo. The literature review you used to do by reading. Many of these offloads are good. Some are great. None are free. Every one of them trains your brain to expect to be carried next time. The cognitive equivalent of taking the elevator one floor up because, well, the elevator is right there.

In 1983, Lisanne Bainbridge wrote about the irony of automation in cockpits (Letter 73). The more you automate, the less prepared the human is to step in when the automation fails. She was writing about pilots. She was writing about all of us.

The model is right most of the time. That's the problem. The model is right just often enough that you stop checking. The moment you stop checking, you stop learning. The moment you stop learning, you stop being able to catch the model on the day it's confidently, beautifully, catastrophically wrong.

And the bench is empty, because you spent the last three years quietly choosing not to train.

The Next $100B Market (and the Next Public Health Crisis)

I don't think this becomes a crisis tomorrow. I think it becomes one slowly, then suddenly, the way obesity did. Quietly between 1970 and 1995. Loudly after.

I also think it becomes a market. A big one.

Imagine the cognitive equivalent of what the fitness industry built between 1980 and 2020. Apps that force you to think slowly. Coaches who train your attention the way trainers train your hamstrings. Schools that re-teach deep reading after a generation lost it to scrolling. Corporate programs that audit and report your team's cognitive endurance the way they currently audit lines of code. Insurance discounts for verified daily reading habits. A Strava for hours spent away from a screen. The Peloton of writing-by-hand.

I'm half-joking and half-not. The fitness industry is $100B+ in revenue every year because we collectively broke our bodies and decided we wanted them back. The brain is more important than the body. The same forces will build the same industry. We are watching its first decade.

The companies that figure this out before everyone else will have an unfair advantage. Not because their employees use AI more. Because their employees can still think on the day the AI hands them an answer that's polished, plausible, and dead wrong. That's the only AI competitive advantage that compounds.

The Cognitive Gym

If we're going to build the gym, what's in it?

Cal Newport recently published a piece in the New York Times arguing exactly this case, and he proposed five components for a basic cognitive fitness routine. I think the framework is right. Let me translate it into operator language.

1. Read every day. 30 to 50 pages. At least one book in three "hard."

This is your base layer. The cardiovascular minimum. Reading is the only activity that consistently rewires neural regions for deep, complex thought. Maryanne Wolf, the cognitive neuroscientist, calls this "deep reading," and she has the brain scans to prove it. Doesn't matter if you start with trashy fiction. The act of holding a single internal target for forty minutes is the rep. Build to a book in three that's actually hard, the way you'd build to a heavier weight.

Scrolling Twitter for two hours does not count, even if the word count is the same. That's the cognitive equivalent of pacing while eating chips.

2. Don't avoid writing. Especially the writing AI can do for you.

This is your gym workout. Writing is physiologically hard. Your hippocampus pulls facts, your prefrontal cortex organizes them, Broca's area narrates, your spatial memory orients the whole thing on the page. It's an improbable symphony. That's why it feels like effort. That effort is the entire point.

Your instinct, when you face a blank page, will be to ask Claude. Resist it. Especially for low-stakes daily writing. Reframe the strain like the burn in a squat. The discomfort is the signal that the muscle is being built. Then, after you've written your draft, open the model and compare. Use it as the editor, never as the ghost.

3. Take thinking walks. Phone in the bag, ringer on, hands free.

Thirty minutes. Once or twice a week. One target in your head, professional or personal. The exercise is turning attention inward and keeping it there. We are very good at locking onto an external target (a tiger, a screen, a notification). We are dangerously out of practice at locking onto an internal one (an idea, a question, ourselves). Thinking walks are the only training I know of for the inner mind's-eye.

Journal one sentence when you get back. The act of compressing the walk into a written line is the second rep.

4. Leave the phone in the kitchen.

This one will feel weird. That's because the "constant companion" mode of phone use is a business model, not a feature. The phone with you at all times exists because of the social-media revenue equation, not because of any law of physics.

When you're home, plug it in somewhere you'd have to walk to. Ringer on, so emergencies still get through. Then go cook, read, sit with your kids, watch a show. Notice the lift. People who try this report a kind of clarity they hadn't felt in years. That's not magic. That's just the absence of a thousand small short-term-motivation pings every hour, each one quietly draining the muscle you'd otherwise be using.

5. Master a hard skill.

A real one. Guitar, judo, chess, knitting, pottery, woodworking, surgery, jazz piano. The criteria: it requires sustained focus to improve, and it gives you clear feedback that you are improving. (Golf counts. Doom-scrolling doesn't.)

The hard skill trains the long-term motivation system to outvote the short-term one. Once you've felt the deep reward of mastering something difficult, the short-term pull of yet another scroll session has competition. That competition is half the battle.

What Companies Will Do (Whether They Realize It Yet or Not)

I expect every serious company to have a cognitive fitness policy by 2035. The way every serious company now has a wellness policy. The way every serious company in 1985 didn't have one and we now consider that ridiculous.

It will look something like this.

Phone-free meeting norms (already happening in scattered places). Reading time built into the workweek the way Google's "20% time" used to be. "No-AI Mondays" or hand-drafting requirements for senior strategic work, so the seniors don't atrophy into the same plateau as the juniors. Hard-skill development budgets, alongside the existing learning budgets that mostly fund LinkedIn Learning. Walking-meeting policies. A quiet metric on the engineering dashboard tracking how often code is shipped without anyone having read it carefully.

This is the same logic as Letter 85's "AI Verification Analyst": the entry-level job changed shape. Cognitive fitness is the same insight at the whole-org level. Production is cheap. What's expensive is the company whose senior people can still think when the machine gets it wrong.

The CFO cutting that "training budget" line right now is the same CFO who, in 2030, can't find anyone in the building who can defend a decision under pressure. That's the loan I described in Letter 85, but for the brain instead of the headcount.

What to Do Monday Morning

Don't try to install all five components at once. You'll quit by Thursday. The whole point is sustainability.

Pick one.

Easiest start: plug your phone in the kitchen every evening this week. Ringer on. Go about your night. That's it. Notice how the evening feels by Friday. Most people are stunned. (I was stunned)

Medium start: read 15 pages tomorrow before opening any app. Anything. A romance novel. A magazine. A boring corporate book your boss recommended. Just 15 pages, sustained, on one thing. Build to 30.

Hardest start (and the one I'd push on if you're a knowledge worker): write your next email from scratch. No AI. Even if it takes you eleven minutes instead of two. Notice what your brain feels like at minute nine. That feeling is the muscle waking up.

Do one. For 30 days. That's the program.

If you're a leader, do one of those for yourself first. Then introduce one into your team's week. Not five. One.

Back to the Kitchen

I memorized my mother's phone number again last weekend. Took me twenty minutes. It felt stupid. It felt like medieval cosplay.

It also felt like the first time in a year I'd asked my brain to hold something, instead of asking the cloud to hold it for me.

The gym is open. The membership is free. The hard part is the same as the physical gym: you have to put down the device and walk in.

If you don't, your judgment atrophies. If your judgment atrophies, the model wins. Not because it's smart, but because there's nobody left in the room who can catch it on the day it isn't.

That's the bill we're about to pay. And we have about a decade to start paying it down before it compounds the way the obesity one did.

AI is only as good as the human operating it. Right now, we're quietly choosing to stop being good at thinking.

Have a great weekend.

Stay sharp.

— Charafeddine (CM)