Use it or lose it. I've repeated this for years, and it keeps being true: the brain is a muscle, and disuse costs you strength.
Now the evidence is arriving. Nature reports on early studies finding that reliance on AI tools degrades the abilities of the people using them. Physicians lose diagnostic accuracy once the assistant is taken away, and software engineers lose fluency in the code they no longer write themselves (Is AI ruining our skills?, June 2026).
The mechanism is familiar. Machines did not weaken our bodies by being evil; they weakened them by being convenient. We stopped walking, stopped lifting, stopped carrying, and then we built gyms to put the effort back in on purpose.
Cognitive offloading works the same way. Every summary you don't read, every proof you don't follow, every function you don't debug is a rep you didn't do. The output still ships. The muscle still shrinks.
So here is the prediction: first we built gyms to fight physical atrophy. Soon, we may build mental gyms to fight cognitive atrophy.
Not brain-training apps chasing high scores, but deliberate, effortful practice at the things we've handed over: reading a hard paper unassisted, doing the derivation by hand, writing the module without autocomplete. Difficulty as a feature, not a bug.
Until those gyms exist, you have to program your own workout. Keep a few tasks you always do the hard way.