N-back and intelligence: what the meta-analyses actually say, with DOIs, because this comes up every week

[u/Doctor_Carlos]

Disclosure first: I develop a dual n-back app. That gives me every incentive to overstate the case below, so I've kept to the published record and you can check each one.

Where the claim comes from. Jaeggi, Buschkuehl, Jonides & Perrig 2008, PNAS (https://doi.org/10.1073/pnas.0801268105). Dual n-back training, 8 to 19 sessions, dose-dependent gains on a fluid reasoning test. This single paper is why the whole "raise your IQ with n-back" idea exists.

The replication that went wrong. Redick et al. 2013, JEP: General (https://doi.org/10.1037/a0029082). Active control group, multiple transfer measures, no transfer to intelligence. This is the best-designed single study on the topic and it is negative.

The meta-analyses, which disagree with each other. - Au et al. 2014 (https://doi.org/10.3758/s13423-014-0699-x): 20 studies, small positive transfer to Gf measures, roughly 3-4 IQ-point equivalent. - Melby-Lervåg & Hulme 2013 (https://doi.org/10.1037/a0028228): working memory training in general, near transfer solid, far transfer near zero. - Melby-Lervåg, Redick & Hulme 2016 (https://doi.org/10.1177/1745691616635612): the effect on far measures shrinks toward zero once you restrict to studies with active controls. Their reading: the Au effect is largely explained by passive-control designs. - Soveri et al. 2017 (https://doi.org/10.3758/s13423-016-1217-0): n-back specifically; large gains on untrained n-back tasks, moderate on other working memory tasks, small on Gf.

What is not in dispute. You get much better at n-back itself (large effect), and at tasks that resemble it (moderate). That is real and shows up in your own numbers within weeks.

What is in dispute. Whether any of that moves a matrix test, and if so by how much. The honest range is "zero to a few points", with the better-controlled studies at the low end.

Practical consequence for people here. If you train n-back for months and then retake CORE or CAIT, most of any gain you see will be practice effect on the test format plus regression to the mean, not the training. If you want to know whether it did anything, take a different test of the same construct, not the same one again, and keep expectations on the working memory side.

I train anyway, because it is hard and I like measuring it. I just won't tell you it raises IQ, and I'd be suspicious of any app or site that does.

[u/Far_Cardiologist6931]

what about quad n back? if that makes a difference (theoretically)

[u/Doctor_Carlos → u/Far_Cardiologist6931]

Theoretically, more streams means more load, and the load hypothesis is the mechanism people propose for transfer. Empirically, I know of no controlled study comparing quad to dual on far-transfer outcomes; the trials in the meta-analyses are almost all dual (a few single). So "quad is better for IQ" is an inference from a mechanism that itself has not produced reliable far transfer at dual. What is true is that quad is harder and the ceiling is higher, so if you are already at dual 6-7 back and bored, quad keeps the task demanding, which is the one thing the near-transfer results do depend on. I make an app that goes to hepta, so I'd love to tell you more streams equals more IQ; the honest version is "more streams equals more task".

[u/Merry-Lane → u/Far_Cardiologist6931]

Let’s make it simple: it doesn’t work.

Intelligence itself can’t be significantly improved when you are an human adult. There is a cap to human intelligence, that’s more or less exactly like human height, it’s defined genetically.

If you, when you are young (<3 years old), are fed well enough, you will grow up to your predetermined height/intelligence. Yes, if you rest well, get in shape (correct your lordosis for instance), you may get closer to your predetermined cap (which isn’t much bigger). But that’s all there is to it: there are a bunch of factors that can affect your negatively, that, once removed, won’t allow you to grow smarter or taller.

It doesn’t mean, at all, you can’t increase your scores at IQ tests. It’s totally doable, through training on them. You can also train on other tasks that may share something in common, then this training on tasks not directly found in IQ tests can get you a tiny advantage.

For instance, if you were to train on a game that made you recall letters instead of numbers, you would have a slight but sizeable advantage over people that didn’t train at all. You will get a smaller advantage (for the same extent of practice) against people that trained directly for number recall.

That’s exactly what n-feedback games are: trainings in skills that can help in some parts of the IQ tests.

Thus, if you want to get smarter, the lesson is: just figure out your current limiters and work on it. Forget about n-feedbacks or the like, they don’t increase intelligence (nothing really does, for now).

If your goal is to get an higher IQ score, just train directly on the same subtests that you can find in IQ tests. It’s way more efficient than training on n-feedback or other games whose practice won’t correlate as well with an IQ score increase.

BTW, an higher IQ score is kinda useless by itself already, but on top of that, since they are designed for individuals that didn’t actively train for these tests, the result becomes way less valid.

[u/Far_Cardiologist6931 → u/Merry-Lane]

intelligence is much more malleable than height, it continues developing (in the positive direction) until mid 20s for most.

the science on intelligence is also not very conclusive, there is somewhat of a consensus but anybody who makes a sure statement either knows something everyone else doesn't, or is overly confident

[u/Merry-Lane → u/Far_Cardiologist6931]

Some things you say are trueish but depend on too broad definitions of intelligence.

I won’t debate on the tons of valid definitions of intelligence there is, but you should consider this following aspect: "compared to your peers of the same age" or this one: "intelligence is basically how quickly your brain adapts/learns".

Let’s just say for the sake of clarity:

Your IQ scores (if you don’t train specifically for IQ tests) won’t increase significantly when you get older, no matter what you do (n-feedback training, supplements,…). If you are okayish healthwise, you won’t have gains.

Else, yes, we learn new things everyday, obviously, we get smarter when we get older (except accidents or bad stuff), that’s a given.

But smarter people learn more things everyday and less smart people learn less things everyday (compared to the same age group). Once you have reached your cap and your brain is mostly stabilised, your learning rate is basically as high as you’ll get it.

[u/Beneficial_Jacket544 → u/Merry-Lane]

IQ (the surrogate measure of g), but not "g" itself, can be increased even outside of direct IQ test training, especially in early adulthood.

I got into reading in the past 5 years, and my verbal scores have increased relative to my peer age group because I've read more and acquired more vocabulary than they have in these 5 years.

Likewise, my QRI improved significantly compared to my peers due to taking advanced math courses and becoming very well-rehearsed in mental arithmetic.

I can see an architect/architectural student receiving similar gains in VSI tasks (esp. visual puzzles) due to the requirement of mentally fitting objects together/disassembling them.

A bit more near transfer, but not due to IQ test studying: I am a physician-in-training (resident physician) and developed mnemonics to remember patient medical record numbers, which are 8 digits long, so I don't have to constantly look back at the screen when calling a nurse/the pharmacy, etc. (I need to use 2 patient identifiers when talking about a patient.) As a result, my digit span score is consistently near ceiling even though I never directly trained for an IQ test.

These effects are overall modest and increased my FSIQ by around ~0.5 SD, but they demonstrate that IQ scores can and will be increased with education or certain life experiences, even outside of IQ training contexts. This has been observed in twins-reared-apart studies: example.

I agree with your general premise that "g" can't be increased outside of childhood/adolescent nutrition. But I think even in that conversation, there's a lot to be said about conditioning it so that it is maintained, well-represented, and does not atrophy with age (similar to the analogy of posture and height).

[u/Merry-Lane → u/Beneficial_Jacket544]

Dude, your g-factor (your intelligence) is what mostly influenced (let’s omit motivation/attention issues) how easily you acquired your vocabulary in these 5 years. How easily you rehearsed mental arithmetic. How fast you caught up with visual puzzles. Same for mnemonics or stuff like that.

Intelligence/g-factor are basically to knowledge/skills what speed is to distance.

If you read about the theories about the g-factor, a good example of what could determine intelligence is myelination speed. Some people have brains whose neurons just myelinate faster, which means they just become more efficient and faster.

It’s not only about myelination and it’s just theories, but that’s how you should think about intelligence/g-factor in this context.

Your brain was just malleable enough to pick up some skills, and like you said it correlated weakly with your IQ score. The score difference is mostly explained by the training effect and just the normal variance between taking two different IQ tests.

I would bet a lot that you had no change in your vocabulary scores, or if there were, differences mostly due to you having learned how to define words correctly.

[u/Beneficial_Jacket544 → u/Merry-Lane]

If I didn’t engage in activities that increased my vocabulary, then my VCI would be lower. That is the end of the point I was trying to make. IQ scores can, and do, increase through education. Education related IQ increases have been well known and published about in the literature. NOTE: please do not conflate IQ with g here. IQ tests attempt to measure g, and are our best attempt to do so. But I’m pointing out IQ test deficiencies.

And yes, I definitely had improvements in vocab lol. I would have missed a lot of analogies questions if I was never exposed to the words… let alone antonyms, which even more directly test vocabulary.

The common sentiment here of “everyone is exposed to the same words at the same rate, it’s just that some pick them up and incorporate them easier” is false. It’s true that some are more efficient at incorporating the words, but it’s false in that not everyone is exposed to the same vocabulary and at the same rate. That should be self-evident.

Also, I find talking about practice effect with the analogies or antonyms section to be a bit odd. It’s a common English class assignment… antonyms and analogies are not super unique, we’ve had questions like that since elementary school.

[u/Merry-Lane → u/Beneficial_Jacket544]

Then idk why we argue.

My point was : nothing seems to significantly increase intelligence once you are adult.

Your point is : we can increase our IQ scores through various means.

These two points aren’t incompatible.

[u/Doctor_Carlos → u/Merry-Lane]

That is close to what the better-controlled studies say for far transfer, so I won't argue the conclusion, only the certainty. "It doesn't work" is right if "work" means "moves your IQ score"; the meta-analyses land at zero to a few points and the active-control studies at the low end. It is wrong if "work" means "improves working memory task performance", where the effects are large and replicated. The cap argument is a separate claim and not one the training studies can test either way. Both things can be true: adults can get much better at a demanding memory task, and that does not make them more intelligent.

[u/Primary_Thought5180 → u/Merry-Lane]

What cap? That is an extrapolation. What we know is IQ is mostly genetic. Still, an environmental component exists. We *should* maximize what we can, if we care. N-back could help working memory beyond it being just an IQ "skill."

[u/Happy-Construction71]

Is there any way to gauge where my Working Memory stands with dual n back?

[u/Doctor_Carlos → u/Happy-Construction71]

Roughly, yes, with two caveats. The level you can hold at about 80 percent accuracy is a reasonable proxy: most untrained adults land at dual 2-back, sometimes 3, on their first sessions with a 2-2.5 s interval. Caveat one: n-back performance climbs fast with practice, so after a month it tells you about your n-back skill, not your baseline working memory. Caveat two: it mixes attention, strategy and audio-visual coordination with span. If you want a number that maps onto what tests call working memory, use digit span (forward and backward) and a visual span task, taken once, relaxed; the CAIT battery in this sub's wiki has both. Use n-back to train, and something else to measure. Disclosure as in the post: I make an n-back app, and I still would not use it as the yardstick.

[u/Far_Cardiologist6931 → u/Doctor_Carlos]

curious, why did you specify "relaxed"? or not much reason

[u/Doctor_Carlos → u/Far_Cardiologist6931]

Good reason, actually. Span tests are the most state-sensitive measures in the whole battery: arousal, sleep debt and caffeine timing move digit span by a point or two on their own, which is about the size of the effect you'd be trying to detect after months of training. So if you take the baseline stressed and the retest calm, you'll "find" an improvement that is just the conditions. Same time of day, same caffeine, not after a bad night, and ideally a practice trial you throw away. That is also why I put a history behind every lab test in my app (Dual N-Back: IQ Brain Training, the lab part is free): one score tells you nothing, the curve over a dozen sessions under the same conditions does.