Can you train your IQ? What the research says
The short answer: test performance yes, the underlying intelligence hardly at all, as far as current evidence goes. That sounds like hair-splitting, but it is the core of the whole debate, and anyone with a test coming up should know the difference.
The trigger: dual n-back, 2008
In 2008 Susanne Jaeggi and colleagues published a study in PNAS that caused a stir. Participants trained a working-memory task, dual n-back, for a few weeks and afterwards scored higher on a test of fluid intelligence, the ability to solve new problems without prior knowledge. The longer the training, the larger the gain. It was the first serious evidence that a trainable module could raise the general factor of intelligence.
The study had weaknesses that were worked through in the following years: small samples, a passive control group that did nothing at all, and intelligence tests shortened under time pressure. Nevertheless it launched a wave of replications and an entire industry.
The meta-analyses
When many studies with conflicting results exist, the meta-analysis that pools them all is what counts. For working-memory training there are several, and they arrive at a consistent picture.
- Melby-Lervåg and Hulme (2013) found improvements in the trained domain but no transfer to verbal ability, reading or arithmetic. The effect on nonverbal intelligence was small and disappeared once only studies with active control groups were considered.
- Au et al. (2015), with a narrower selection, found a small positive effect on fluid intelligence, in the range of three to four IQ points. That is the most optimistic serious estimate.
- Melby-Lervåg, Redick and Hulme (2016) replied with an extended analysis: in studies with active control groups, a group that trains a different task for the same amount of time, the transfer effect goes to zero. The difference from Au et al. lies almost entirely in which control groups are admitted.
- Simons et al. (2016) examined the whole brain-training industry in "Do Brain-Training Programs Work?" and found: people get better at the trained tasks, somewhat better at similar tasks, and practically no better in daily life or general intelligence. The same year the Federal Trade Commission fined Lumosity two million dollars for unsupported advertising claims.
The pattern is known in the research as near and far transfer. Near transfer, improvement in the task itself and its closest relatives, is robust. Far transfer to the general factor is not. Train dual n-back and you get very good at dual n-back.
What is well documented: the practice effect
There is a second line of research that gets far less attention because it is unspectacular. It deals with what happens when people take the same test, or a similar format, more than once.
The meta-analysis by Hausknecht, Halpert, Di Paolo and Moriarty Gerrard (2007) in the Journal of Applied Psychology covered over 100 samples with more than 100,000 participants. Result: simply retaking a cognitive ability test raises the score by about a quarter of a standard deviation on average. With targeted coaching, learning the item types and strategies, the gain is considerably larger. On the IQ scale with a standard deviation of 15, a quarter of a standard deviation is just under four points, and that is without any strategy, from familiarity alone.
The reason is simple. An intelligence test measures not only the ability to spot a pattern, but also how quickly you understand what the item is asking, how you allocate time and how you handle items you cannot solve. Those components are learnable, and on first contact with a test format they are substantial.
What this means for preparation
Anyone facing an aptitude test, an admission procedure or a Mensa test has two options. The first is to invest weeks in brain training in the hope that a few points trickle through. The evidence for that is thin. The second is to practice the concrete item types of the test until the format holds no surprises. The evidence for that is solid.
Concretely: matrices, number series, figure series, analogies, digit span. Work through each type often enough to know the rule families, under a time limit, with an explanation after every item. Not because it changes the general factor, but because it closes the gap between what you can do and what the test measures.
And working memory?
Tasks like dual n-back, Stroop or Corsi block are not worthless for that reason. They measure functions that correlate with intelligence, in the region of 0.3 to 0.5. As measurement instruments they are reliable, and anyone who tracks their own reaction time or working-memory span over weeks sees something real: sleep, stress and daily form show up in the numbers. Only the expectation that training these functions raises IQ is not supported by the current state of research.
Sources
- Jaeggi, S. M., Buschkuehl, M., Jonides, J., Perrig, W. J. (2008). Improving fluid intelligence with training on working memory. PNAS, 105(19).
- Melby-Lervåg, M., Hulme, C. (2013). Is working memory training effective? A meta-analytic review. Developmental Psychology, 49(2).
- Au, J., Sheehan, E., Tsai, N., Duncan, G. J., Buschkuehl, M., Jaeggi, S. M. (2015). Improving fluid intelligence with training on working memory: a meta-analysis. Psychonomic Bulletin & Review, 22(2).
- Melby-Lervåg, M., Redick, T. S., Hulme, C. (2016). Working memory training does not improve performance on measures of intelligence or other measures of "far transfer". Perspectives on Psychological Science, 11(4).
- Simons, D. J., et al. (2016). Do "Brain-Training" Programs Work? Psychological Science in the Public Interest, 17(3).
- Hausknecht, J. P., Halpert, J. A., Di Paolo, N. T., Moriarty Gerrard, M. O. (2007). Retesting in selection: A meta-analysis of coaching and practice effects for tests of cognitive ability. Journal of Applied Psychology, 92(2).
Frequently asked questions
Can you increase your IQ through training?
Your test score, yes, by several points, through familiarity with the test format. The underlying intelligence, according to the meta-analyses, hardly at all. Brain training and working-memory training mostly improve the trained task itself.
How many IQ points does practice give you?
The meta-analysis by Hausknecht et al. (2007) finds a gain of about a quarter of a standard deviation from retaking a test, which is just under four IQ points, and more with targeted coaching.
Does dual n-back work?
You get very good at dual n-back. Transfer to fluid intelligence does not show up in meta-analyses with active control groups, or only minimally.
IQ Prep drills exactly these item types under test conditions, with an explanation after every answer. Free to try, full version $4.99 one time, no subscription.
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