The Mistake People Make When Their Intelligence Crystallizes
When we age some mental capabilities fade, but others thrive and open up totally new opportunities.
It starts in our mid-30s. We begin to lose muscle mass. It's not an illness—just biology. On average, we shed 8% per decade. We put on weight. Even our motor skills might start to slip. Most people know this, at least vaguely. That’s why we hit the gym more often as we age. Some get leaner, some don’t. Definitely unfair.
Another invisible kind of decline doesn’t help building more acceptance for aging. It’s a mental one. The good thing: In contrast to gaining weight, the change is transactional. We get something else in return.
For nearly a century, scientists have distinguished between two types of intelligence.
Fluid intelligence helps us analyze, reason, and solve problems. Crystallized intelligence is experience-based. It helps us make sense of complexity, spot patterns, and explain things clearly.
In youth, fluid intelligence dominates. We’re fast. We haven’t built much experience yet. But as we get older, the balance shifts. Crystallized intelligence grows—while our analytical edge dulls. Fluid intelligence fades.
I’ve learned a lot in my life. But I only recently came across this research—and it shook me. I’ve always worked with my mind. Over the years I developed a feeling for my capabilities. At least I thought so.
Hiring my former self
In 2020, I hired Arthur. He was 22, sharp as a tack, and focused on cloud engineering. I liked him right away. I knew we'd learn from him—and we did. Six months in, a client extended a contract by $100,000.
For the business, he was gold. For me, not so much. The more he ramped up, the foggier things got. He could see through the complexity—I couldn’t. After every review with him I tried to take 30min break, for processing his ideas. I was excited.
So I picked up algebra again. Hankel matrices, which I’d only known by name, became my dinner reading. I started to get it—why we used them to analyze sensor data. But it took too long. Much longer than it used to, when I studied physiscs.
Eventually, I gave up. I had 25 performance reviews to prep. A year later, Arthur quit. This was shocking. His impact was undeniable. But he left. And it stung. It felt like a piece of my own past capabilities walked out with him.
What about you? Would you be prepared for hiring your former self? I’ll write a piece about every comment I receive.
Exit the speedway
While I was chasing my fluid intelligence, I failed to create a system that helped young talent thrive. Luckily, something else grew: my crystallized intelligence. Through Arthur’s exit I should’ve learned more than any math textbook could’ve taught me.
I’ve come to accept that I’m not the one to write patents anymore. I don’t need to understand quantum computing in detail—even if I passed Quantum Theory 1 twenty years ago. I don’t have the time to digest modern physics today. Or the drive. That’s the odd truth.
Crystallized intelligence is at the wheel now. I focus on the bigger picture, not syntax.
Sure, there’s still a pit in my stomach when a 25-year-old AI engineer flies past me like a Porsche on the interstate. And to be clear: Not only once I caught myself one foot on the gas pedal desperately trying to catch up.
But here’s the thing: sometimes the experienced know a shortcut and exit the speedway. Because we’ve taken that road before. Because we remember the road block some miles from here.
Many more fluid minds might miss the turn. Surprisingly, the next morning, the invite to the “final design decision” meeting shows up in their inbox.
In their 30s and 40s, many people feel the urge to change. Not just because they better know, what they want—but because their brains are changing.
That’s the time to rethink your role. Often associates become leads. Seasoned managers become advisors. I am afraid, HR often doesn’t have a plan how to handle the intelligence shift. I’ve met numerous desperate seniors leaving instead of creating edge for their company—although the facts are known since 1963.
When we realign our work with how we’ve evolved, everybody wins.
We’re more fulfilled. Teams run smoother. More often someone takes the off-ramp—and finds a shortcut.
Thanks for reading!
Yours,
Chris
If you would like to read more about this topic you could take From Strength to Strength by Arthur Brooks or join our community here on Substack.
In Make Work Matter Again, I’ll share how I’m making change meaningful — again and again.
Because work doesn’t stand still — and neither do you.
Your skills grow.
Your habits evolve.
Your life changes. Roles shift. Kids arrive. You relocate. You adapt. You grow.
But let’s be honest:
It’s hard to keep performing when the ground beneath your feet is shaking.
Even superstars can’t keep the show going when an earthquake hits mid-song.
Change is inevitable.
What matters is how we respond.
When life hits, I’ll be here to remind you:
→ Stay ahead.
→ Stay grounded.
→ Stay happy.