Can You Actually Get Smarter? What the Research Says

Two people take the same IQ test twenty years apart. One spent those two decades doing daily memory-game drills, chasing the promise of a faster brain. The other spent them reading widely, picking up a second language, and arguing about politics at dinner. Only one of them actually got smarter in a way that shows up anywhere outside the app they were using.

The research on this is more specific than "yes" or "no," and more useful than either. Some kinds of intelligence grow for decades. Others barely move no matter what you do to them. Knowing which is which changes where you should actually be spending effort.

Key Takeaways

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• Crystallized intelligence, your accumulated knowledge and vocabulary, keeps growing well into your 60s and 70s, while raw processing speed peaks around the end of high school

• Each additional year of education raises measured IQ by roughly 1 to 5 points, confirmed by a 2018 meta-analysis of 142 effect sizes across more than 600,000 people

• Brain-training games reliably improve the trained task and closely related tasks, but large reviews find little evidence they improve reasoning, reading, or everyday performance

• Sleep loss doesn't lower your true ceiling, it drags your performance below it, and getting enough sleep is closer to removing a penalty than gaining an advantage

Why Do Fluid and Crystallized Intelligence Tell Completely Different Stories?

In the 1960s, psychologists Raymond Cattell and John Horn split general intelligence into two parts, and the distinction still organizes how researchers think about this question.

Fluid intelligence is the ability to solve a problem you've never seen before, spot a pattern, or juggle several unfamiliar things in your head at once. Crystallized intelligence is what you've already banked: vocabulary, facts, methods, and an accumulated sense of how things usually work. A large study of 48,537 people by Joshua Hartshorne and Laura Germine, published in 2015, found these two measures peak at completely different points in life. Raw processing speed peaked around the end of high school. Vocabulary didn't peak until people's late 60s or early 70s.

That single finding reframes the whole question. The part of intelligence built from knowledge is the part that keeps growing, and it only grows if you feed it something to grow on.

Does Education Actually Raise IQ, or Just Correlate With It?

For decades this was a chicken-and-egg problem. Do people who are already smart simply stay in school longer, or does school itself raise intelligence?

In 2018, Stuart Ritchie and Elliot Tucker-Drob published a meta-analysis in Psychological Science that isolated the causal question specifically, pooling 142 effect sizes from 42 data sets covering more than 600,000 people. They used three different study designs that each control for the chicken-and-egg problem in a different way: comparing people who scored the same as children but received different amounts of schooling, tracking countries that raised their legal school-leaving age, and comparing children born just before or after a school-entry cutoff date. The three designs produced estimates of 1.2, 2.1, and 5.2 IQ points per extra year of education respectively, giving the commonly cited range of roughly 1 to 5 points. The effect held up across broad categories of ability and was still measurable in people tested in their 70s and 80s, though it shrank somewhat with age at testing.

The authors' own conclusion, worth quoting directly: education is "the most consistent, robust, and durable method yet to be identified for raising intelligence." A few IQ points a year is modest, not transformative, but it's real, and it's the strongest causal evidence in this entire field.

Is Intelligence Actually Fixed by Genetics?

Twin studies consistently find IQ substantially heritable, and heritability rises with age, from roughly 41% at age 9 to around 66% by age 17, according to a 2010 study of 11,000 twin pairs across four countries led by Claire Haworth. On its surface, that sounds like destiny.

It isn't, for a reason most people miss: heritability describes variation within a population at a given time, not the ceiling for any individual. Highly heritable traits still move substantially when the environment changes. Adult height is roughly 80% heritable, and over the 20th century South Korean women grew 20.2 centimeters taller on average, purely from improved nutrition and health, with the same gene pool. Intelligence shows a similar pattern at the population level: average IQ scores rose roughly 3 points per decade through most of the 20th century, a pattern researchers call the Flynn effect, and in several wealthy countries that rise has since reversed. A study of over 730,000 Norwegian men found the decline showed up between brothers in the same family, which rules out genetics as the cause, since genes don't shift that fast within a family. Something in the environment moved first.

Does Brain Training Actually Make You Smarter?

This is where the evidence gets genuinely contested, and where most of the marketing in this space outruns what the research actually supports.

An influential 2008 study by Susanne Jaeggi found that practicing a demanding working-memory task called the dual n-back improved fluid intelligence scores, with larger gains the more days people trained. It looked like proof that intelligence had a trainable bottleneck. Then came the replications. A 2013 randomized, placebo-controlled study by Thomas Redick found participants got substantially better at the n-back task itself and showed no improvement on any measure of intelligence, multitasking, or working memory capacity. The field has argued about this ever since: a 2015 meta-analysis co-authored by Jaeggi found a small positive effect, while other researchers reanalyzing the same data found the effect disappeared once only properly controlled studies were counted.

The broadest, most authoritative review came from a seven-researcher panel led by Daniel Simons, published in Psychological Science in the Public Interest in 2016. Their conclusion was direct: training reliably improves the trained task, improves closely related tasks somewhat less, and shows little convincing evidence of improving distantly related skills or everyday cognitive performance. This is the same evidence base behind Lumosity's 2016 FTC settlement, where the company paid $2 million for advertising cognitive benefits the underlying science didn't support. Brain-training games are a fine hobby. They are not a reliable shortcut to broader intelligence.

What About Sleep and Exercise?

These work through different mechanisms, and the evidence for each is a different strength than most people assume.

Sleep loss doesn't lower your underlying ceiling. It drags your actual performance well below it, specifically hitting sustained attention and working memory, according to a 2010 meta-analysis of 70 studies by Lim and Dinges. Interestingly, that same analysis found reasoning accuracy barely changed under sleep deprivation, which means the damage shows up more in your ability to pay attention long enough to learn something new than in raw problem-solving itself. Getting enough sleep is less a cognitive upgrade and more removing a penalty you were otherwise paying.

Exercise is more contested. A 2023 umbrella review in Nature Human Behaviour, looking only at randomized trials in healthy people, found a small average cognitive benefit that shrank further after accounting for study quality and became negligible once corrected for publication bias. Other researchers have pushed back on that conclusion, and the debate continues. The honest takeaway: move for your heart, mood, and long-term brain health. Don't expect a measurable IQ bump by lunchtime.

Does Your Brain Physically Change From Learning?

Yes, and a well-designed study on London taxi drivers shows exactly how specific that change is.

To earn a license, London cab drivers spend years memorizing roughly 25,000 streets, a notoriously difficult process known as "the Knowledge." Neuroscientist Eleanor Maguire's team found qualified drivers had larger posterior hippocampi than non-drivers, with the size tracking years on the job. The obvious objection: maybe people with naturally larger hippocampi are simply more likely to become taxi drivers. A follow-up study tracked 79 trainees and 31 controls over three to four years. At the start, no group differences existed. By the end, only trainees who actually passed the licensing test showed hippocampal growth. Trainees who failed, and the control group, showed no change at all.

The brain adapts physically to sustained, demanding learning. But the adaptation is narrow: the same study found qualified drivers performed worse than controls on one test of complex visual memory unrelated to navigation. You get a better map of London, not a generically better brain. This same specificity shows up in critical thinking: practicing one kind of reasoning sharpens that reasoning, not reasoning in general.

The Bottom Line

Can you get smarter? Yes, in the way that actually matters for daily life. The strongest evidence points to sustained education and real learning, not drills designed to train "the brain" as an abstract muscle. Crystallized knowledge keeps compounding for decades after fluid processing speed has already peaked, and that compounding only happens if you keep feeding it.

This is the part of intelligence Morso is built around. Type any topic and get a structured, bite-sized lesson in about 30 seconds, explained through analogy so new material connects to what you already know, with a practice quiz that tests whether it actually stuck. It won't raise your IQ by itself, and any product that claims otherwise deserves the same scrutiny Lumosity got. What it will do is help you bank a little more real knowledge every day, which is the one part of intelligence the evidence says keeps paying off well into your 70s. Try it free on any topic.

For the research on why testing yourself specifically builds knowledge that lasts, see active recall: what it is and why it works. For the fuller, honest breakdown of what brain-training apps can and can't do, see best brain training apps in 2026.

Sources

Hartshorne, J. K. and Germine, L. T. (2015). When Does Cognitive Functioning Peak? The Asynchronous Rise and Fall of Different Cognitive Abilities Across the Life Span. Psychological Science, 26(4), 433-443.

Ritchie, S. J. and Tucker-Drob, E. M. (2018). How Much Does Education Improve Intelligence? A Meta-Analysis. Psychological Science, 29(8), 1358-1369.

Haworth, C. M. A. et al. (2010). The Heritability of General Cognitive Ability Increases Linearly From Childhood to Young Adulthood. Molecular Psychiatry, 15(11), 1112-1120.

Simons, D. J. et al. (2016). Do "Brain-Training" Programs Work? Psychological Science in the Public Interest, 17(3), 103-186.

Federal Trade Commission (2016). Lumosity to Pay $2 Million to Settle FTC Deceptive Advertising Charges.

Lim, J. and Dinges, D. F. (2010). A Meta-Analysis of the Impact of Short-Term Sleep Deprivation on Cognitive Variables. Psychological Bulletin, 136(3), 375-389.

Maguire, E. A. et al. (2000). Navigation-Related Structural Change in the Hippocampi of Taxi Drivers. Proceedings of the National Academy of Sciences, 97(8), 4398-4403.