Evidence

How to increase your IQ: what actually works

Brain-training apps, dual n-back, supplements, music, sleep. Sorting the interventions with evidence behind them from the ones with marketing behind them.

First, decide which question you are asking

Two different things get called “raising your IQ”, and confusing them is why the topic produces so much noise.

The first is raising your score on a test. This is straightforward and not particularly interesting. Do thirty matrix items, learn the handful of rule families they are built from, and your next matrix score goes up. Nothing about your reasoning changed; you learned the format.

The second is raising the underlying ability that the test is sampling — the thing that would show up on a test you have never seen, in a domain you have not practised. This is what people mean when they ask, and it is much harder.

Almost every commercial product in this space sells the first and implies the second. The test for whether an intervention did the second is called far transfer: does the gain show up on a task that shares no surface features with the training? Far transfer is where nearly every brain-training claim dies.

What has the strongest evidence: more schooling

The best-supported intervention for raising measured intelligence is unglamorous: staying in education longer.

The evidence here is unusually good because it does not rely on volunteers. Several countries have raised the school leaving age by law, which creates a natural experiment: two cohorts born a year apart, one legally required to stay an extra year, otherwise comparable. Comparisons of this kind, together with regression-discontinuity studies of school entry cutoffs and analyses of instructional time, converge on a gain in the region of one to five IQ points per additional year of schooling.

That is a real effect on a real measurement, and it is larger than anything the supplement aisle has produced. Two caveats keep it honest. It is measured at the population level, so it tells you what an extra year does on average rather than what it will do for you. And there is a live argument about how much of the gain is broad reasoning versus the specific skills that schools teach and tests happen to reward.

What has the weakest evidence: commercial brain training

The brain-training industry rests on a specific claim: that repeatedly practising a working-memory task produces gains that transfer to general reasoning.

The claim had a plausible starting point. Early studies of dual n-back training reported transfer to fluid intelligence measures, and the finding was genuinely exciting. What happened next is a familiar pattern in psychology. Larger studies with active control groups — where the comparison group also does something demanding, rather than nothing — shrank the effect. Meta-analyses that accounted for publication bias shrank it further. Studies that used more than one outcome measure found gains on the trained task and little else.

The current state of the evidence is that people get better at the exercises they practise, and that this improvement does not reliably show up anywhere else. In 2014 a large group of cognitive scientists signed a public statement to this effect; a competing statement was signed by another group; the dispute has not been resolved in favour of the industry in the decade since.

This does not mean the games are worthless. They are engaging, and enjoying a mentally demanding hobby is not a bad thing. It means the specific promise — buy a subscription, raise your intelligence — is not supported.

The interventions that remove a handicap rather than add an ability

A large share of what looks like IQ improvement is actually the removal of something that was suppressing performance. This distinction matters, because it sets a ceiling: you can recover what poor conditions cost you, and that is not the same as exceeding your own baseline.

Sleep. Restriction to five or six hours a night produces measurable declines in working memory and reasoning within days, and people are notoriously bad at noticing their own impairment. Catching up on chronic sleep debt can raise a test score noticeably. It is not making you smarter; it is stopping you from being temporarily worse.

Aerobic exercise. Regular cardiovascular exercise has reasonable evidence for cognitive benefit, with the clearest effects in older adults and in people starting from a sedentary baseline. Effects on executive function are more consistent than effects on fluid reasoning specifically.

Nutritional deficiency. Correcting iodine deficiency in populations where it is endemic produces substantial gains in child cognitive development — among the largest documented effects on population IQ. Correcting a deficiency you do not have produces nothing, which is why general supplementation in well-nourished populations shows so little.

Lead and other neurotoxins. Removing environmental lead exposure produced measurable population-level gains across several countries. Again: not an enhancement, the removal of a harm.

The claims that do not hold up

The Mozart effect. The original 1993 finding was a small, brief improvement on a spatial task after listening to a Mozart sonata. It was never a finding about IQ, it did not last more than about fifteen minutes, and later work attributed it largely to arousal and mood rather than to the music. The version that reached the public — play classical music to babies to raise their intelligence — was never what the study showed.

Nootropic supplements. The category covers everything from caffeine to compounds with no human trials. Caffeine and, in some people, creatine have modest short-term effects on alertness or working memory. Nothing in the consumer supplement market has good evidence for durable gains in reasoning ability.

Learning an instrument or a second language. Both are strongly correlated with higher cognitive scores. Both are also strongly correlated with having the time, money and schooling to pursue them. Randomised studies that address the selection problem find much smaller effects than the correlational literature implies.

What practice actually buys you

Practising test formats is worth discussing on its own terms, because the honest answer is more useful than either the marketing version or the dismissive one.

Practice on reasoning tests produces real, reliable gains of several points on the practised format, most of it on the first repeat and diminishing quickly after that. The gains are largest for people unfamiliar with the format and for item types with a small number of underlying rules — matrices especially.

This is genuinely useful if you have a supervised test coming up and you have never seen a matrix item before, because in that situation part of what the test is measuring is your unfamiliarity rather than your reasoning. Removing that is fair and sensible.

It is not useful if you want to know your baseline. Taking four online tests and reporting the highest is a way of measuring your best day and your accumulated format practice, not your ability. If you want a clean read, one attempt at an unfamiliar test tells you more than five attempts at a familiar one.

The honest summary

If you want the shortest defensible version:

• Stay in education longer. The best-evidenced intervention, worth a few points a year, measured at the population level.
• Fix your sleep. Recovers what deprivation costs you, which can be several points.
• Exercise regularly. Modest, real, clearest for executive function and in older adults.
• Correct actual deficiencies. Large effects where a deficiency exists, none where it does not.
• Practise the format before a test that matters. Real gains on that format, no gain in the underlying ability.
• Skip the subscriptions and the supplements. The transfer evidence is not there.

And a final point that is easy to lose. IQ predicts a moderate amount of variance in outcomes people care about, and chasing points is a strange use of attention when the things that shift outcomes more — what you know, who you know, what you finish — are far more responsive to effort.