Is IQ Fixed? What the Science Actually Says in 2026

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When I was 13, failing all eight of my classes in Alaska, my dad looked at me and said, “You gotta be the dumbest kid in the family.” For most people a line like that becomes a verdict you spend the rest of your life either proving or quietly believing. So when people ask me the question that probably brought you here, can you increase your IQ, or is the number you were handed at birth the number you die with, I think about that kid. The same kid later read around 250 books in 18 months and now studies Spanish four to eight hours a day for the fun of it. The science in 2026 has an answer, and it is more interesting than a flat yes or no.

Can you increase your IQ, or is it locked in your genes?

Start with the thing everyone gets wrong. You have heard that intelligence is mostly genetic, and that part is roughly true. Twin and adoption studies put the heritability of adult IQ around 0.6 to 0.8, and it actually climbs as you age. The mistake is what your brain does next. It hears “80% genetic” and translates it into “fixed.” Those are not the same sentence, not even close.

Here is the analogy that breaks the spell. Height is about 80% heritable too, and yet the average person today stands several inches taller than their great-grandparents, because nutrition got better across the whole population. Genes set the range. The environment decides where inside it you land. Heritability tells you why people in the same environment differ from each other. It says almost nothing about how high you personally can climb when you change the inputs. So the honest answer to “is IQ fixed” is no, and the people who told you otherwise were misreading a number.

The proof that IQ moves: whole populations already did it

You do not have to take my word for it. Across the 20th century, IQ scores in the developed world rose about 3 points every decade. Roughly 30 points over a hundred years. A researcher named James Flynn documented it so thoroughly they named it the Flynn effect. Nobody’s DNA changed in three generations. The genes stood still and the scores climbed, because schooling spread, nutrition improved, and daily life got more abstract and demanding. Population intelligence is not a fixed quantity. It already moved, on a massive scale, inside living memory.

Zoom from the population down to the individual and the same picture holds. In 2018, Ritchie and Tucker-Drob ran a meta-analysis pooling 42 datasets and more than 600,000 people, asking one clean question: does staying in school actually raise intelligence, or do smart people just stay in school longer? The answer was roughly 1 to 5 IQ points for every additional year of education, and the gains were durable. That is not a tutoring trick that fades by summer. That is the machinery responding to load.

The catch nobody tells you: two kinds of intelligence age differently

Now the nuance that makes the whole question sharper. You do not have one intelligence; you have two engines, and they run on different clocks.

• Crystallized intelligence is everything you have learned: your vocabulary, your facts, your hard-won pattern library. It keeps climbing into your 60s and 70s, which is good news if you are a knowledge worker.
• Fluid intelligence is the part that reasons through a problem you have never seen before, holds the moving pieces in your head, and spots the connection. That is the raw horsepower, and left alone it tends to peak in your late 20s and slide from there.

That slide is the thing you actually feel. You watch a younger colleague connect two ideas you should have connected first, and a quiet voice says maybe you have peaked, maybe this is just what getting older feels like. For an analytical person who has always traded on being sharp, that voice is harder to sit with than any blank spreadsheet. And fluid reasoning is exactly the engine recent training research is trying to rebuild. Which brings us to the landmine.

Why most “brain training” cannot raise your IQ

Here is the thing. The reason you are right to be skeptical of brain games is that almost all of them fail one specific test, and it is the only test that matters. It is called transfer. In 2010, Adrian Owen and colleagues ran a study published in Nature with 11,430 participants doing online brain training. The result was brutal and clean: people got better at the games they practiced, and those gains did not carry over to general thinking at all. You can become a god at a memory game and still blank in the meeting that pays your mortgage.

This is the wall the brain-game industry hit and then papered over. Lumosity sold the dream that matching tiles made you smarter at life. In 2016 the FTC fined them $2 million for it, because the transfer was never there. So if a tool’s whole pitch is “play our puzzles and get smarter,” and it never shows the gains moving off the screen and into a new kind of problem, you are right to walk. That is the real objection to the whole category, and most of the time it is correct.

What actually transfers: train the engine, not the party trick

So the question was never really “can you train your brain.” Of course you can. You trained it to read this sentence and run a P&L. The honest question is narrower: can you train it in a way that transfers to problems you have never seen? One approach stands apart from the puzzle pile, and it comes from a corner of behavioral science most people have never heard of.

It is called Relational Frame Theory. The core finding is that the most fundamental operation your mind performs is relating one thing to another. This is the same as that. This is the opposite of that. This is more than, before, part of, caused by that. Those relations are the atoms of language and reasoning. Stack them fast enough and automatically enough and you get what we loosely call fluid intelligence. The reason this matters is that when you train the relating itself, instead of one fixed puzzle, you are sharpening the engine every novel problem runs on. In a 2016 study, Cassidy, Roche and colleagues trained children on relational skills and measured genuine rises in their full-scale IQ, gains of roughly one standard deviation per child. It is a smaller body of evidence than the Flynn data, and I will not hand you a guaranteed point count. But the mechanism is the right one. You train what reasoning is built from, not a trick that lives on one screen.

That bet is what I built CortexSurge on. It trains all 19 relational frames to fluency across more than 3,700 adaptive levels, holding you near 85% accuracy so each round is just hard enough to grow you and never so brutal you quit. It scores you on one number, the Cortex Index, so “am I getting sharper” stops being a feeling and becomes something you watch on a chart. And the first time that line ticks up instead of down, the quiet voice that told you you had peaked goes quiet for good. Most people say something clicks around 15 to 25 hours in. Real, measurable gains tend to show up over two to three months at four or five short sessions a week. Not a game you beat, a protocol you run.

A mind you forge, not one you inherit

Back to that 13-year-old failing every class. I did not become someone who reads 250 books in 18 months and learns languages for sport because a gene switched on. I became that person on purpose, one loaded session at a time, once I stopped treating my mind as a fixed allotment and started treating it as the one asset I could compound for the rest of my life. That is why this matters more than any single test score. The person whose intelligence keeps climbing while the room slows down does not get there by accident. They decided their mind was forged, then they did the reps.

If you want the wider map of how I think about focus, return on effort, and building a mind that compounds, start here. Then come back and put a baseline number on the board.

So do this, in order, this week. Run the free assessment and write down your Cortex Index, today, before you change a thing. Then do one training round a day for thirty days and check the number again. You are not stuck with the mind you were issued. The science is clear, the dad who called me the dumbest kid was wrong, and the only thing standing between you and a sharper version of yourself is the decision to start the reps.

Related reading: Brain Fog Is Costing You Money: How to Think Clearly Under Pressure, The High Earner’s Daily Routine for Mental Performance, How to Train Your Brain for Sharper Thinking: A Practical RFT Guide.