Although it is popular for people to claim that they don’t know what intelligence is, most people show an interest in boosting their intelligence. Funny, that. These schemes come around every few years: getting babies in the womb to listen to Mozart, taking vitamins and concentration enhancing drugs, counting backwards in the N back procedure: that sort of thing. Doug Detterman, founder editor of Intelligence, who waded through 50 years of this moonshine, said that he was not against finding something, but simply had to note that on close examination all these schemes had turned out to be a disappointment. Many techniques produce some effects, but few generalize and persist.
A common thread in this wishful thinking is that the procedures should be easy and fast: 20 training sessions, a couple of months of practice, that sort of thing. Unlikely. However, a stronger case has been made for that boring activity: staying longer at school. Whenever people intend to waste their time boosting their intelligence with the latest training technique, I tell them to learn something useful like statistics, experimental methods, genetics, computer programming, maths, game theory, physics and even history and philosophy. I don’t for a moment imagine it will boost their intellects, merely give them some content and some tools for thinking. On that note, Tony Flew’s “Thinking about thinking” Fontana, 1975, is a good start.
However, could studying difficult subjects boost intelligence? I looked at this argument some time ago, and came to the conclusion that it probably boosted intelligence by 0.6 IQ points. I was a bit doubtful about it doing any more than that, because we did not have a long data series which would put the matter beyond dispute. I did not accept the authors’ estimate of an enormous 3.7 IQ points per year gain, simply because of a lack of historical data. That is to say, if the Norwegian schooling reform really boosts IQ, then the long data series before and after the reform would show a sustained upward tick in the national intelligence. I haven’t been able to find those data, though they may exist. I give my argument in the link below. You will see that in that post I cover a paper on this topic by Stuart Ritchie and colleagues, of which more below.
However, the caravan moves on, and now we have two papers saying that schooling boosts intelligence. You wait ages for a bus, and then two come along.
Raising IQ among school-aged children: Five meta-analyses and a review of randomized controlled trials. John Protzko. Developmental Review, 46, 2017, 81-101.
There have been 36 RCTs attempting to raise IQ in school-aged children. Nutrient supplementation includes multivitamins, iron, iodine, and zinc. Training includes EF and reasoning training, and learning a musical instrument. We meta-analyze this literature to provide a best-evidence summary to date. Multivitamin & iodine supplementation, and learning a musical instrument, raise IQ.
In this paper, we examine nearly every available randomized controlled trial that attempts to raise IQ in children from once they begin kindergarten until pre-adolescence. We use meta-analytic procedures when there are more than three studies employing similar methods, reviewing individual interventions when too few replications are available for a quantitative analysis. All studies included in this synthesis are on non-clinical populations. This yields five fixed-effects meta-analyses on the roles of dietary supplementation with multivitamins, iron, and iodine, as well as executive function training, and learning to play a musical instrument. We find that supplementing a deficient child with multivitamins raises their IQ, supplementing a deficient child with iodine raises their IQ, and learning to play a musical instrument raises a child’s IQ. The role of iron, and executive function training are unreliable in their estimates. We also subject each meta-analytic result to a series of robustness checks. In each meta-analysis, we discuss probable causal mechanisms for how each of these procedures raises intelligence. Though each meta-analysis includes a moderate to small number of studies (< 19 effect sizes), our purpose is to highlight the best available evidence and encourage the continued experimentation in each of these fields.
The author is looking at controlled trials on which individuals are given intelligence tests before and after programs which are at least two weeks long, in children aged 5 through to pre-adolescence, looking at effect sizes at immediate post-test. No follow-ups are mentioned, not even 6 months later, the usual minimum for a clinical intervention.
The multivitamin study produces such a small effect that it is silly to test it for significance. Protzko says that there was “an incredibly small but significant effect of taking multivitamins on IQ (g = 0.097, 95%CI = 0.006to 0.187; see Fig. 1). The abstract says: “We find that supplementing a deficient child with multivitamins raises their IQ,” which I think exaggerates what was found, which was incredibly small. Furthermore, only 3 of the 17 studies have more than 100 people in the active treatment condition, and that is rather small even for a controlled trial.
Iodine supplementation shows a half a standard deviation gain, but the author is rightly cautious about the papers, saying it only works for iodine deficient children, and also the effect goes down from g 0.5 to g 0.3 when one outlier study is removed. Still a sizeable effect for the target population, though not something which will have general application.
Under “environmental changes” or what I would call experimental enrichment studies, there were no effects for balance and coordination exercises, home academic support as part of the Abecedarian project (bang goes one theory about family environments), reasoning training (rejected because it is too much like “teaching to the test”), executive function training (a slight effect, marred by publication bias) and finally music lessons.
We found that teaching a child a musical instrument raises their IQ by over a third of a standard deviation (g= 0.421, 95%CI = 0.196 to 0.646; see Fig. 5). In addition, there was no evidence for heterogeneity in this sample (Q(5) 4.68,p> 0.466;I2= 0%)
The author links this, speculatively, to rhythm perception and discrimination. However, sample sizes are small, ranging from 10 to 32 children in the training condition.
In his general discussion the author makes a case for the effects of education on intelligence, whilst conceding that because most of the studies are on poor children there is a range restriction which may affect the wider applicability of the results.
Studies supplementing inadequate diets with multivitamins raised IQ. Studies remediating mild iodine deficiency raised IQ. Studies involving teaching a musical instrument raised IQ. After correcting for range restriction, this corresponded to an increase of 4 IQ points in the population.
My conclusion is that Protzko has made a reasonable case, in a carefully argued paper, but everything he reports is about immediate effects, and before coming to any conclusions it would be good to know whether the effects last more than 6 months.
The second paper is:
How much does education improve intelligence? A meta-analysis. EDUCATION AND INTELLIGENCE METAANALYSIS. 2017
Stuart J. Ritchie & Elliot M. Tucker-Drob.
Intelligence test scores and educational duration are positively correlated. This correlation can be interpreted in two ways: students with greater propensity for intelligence go on to complete more education, or a longer education increases intelligence. We meta-analysed three categories of quasi-experimental studies of educational effects on intelligence: those estimating education-intelligence associations after controlling for earlier intelligence, those using compulsory schooling policy changes as instrumental variables, and those using regression-discontinuity designs on school-entry age cut offs. Across 142 effect sizes from 42 data sets involving over 600,000 participants, we found consistent evidence for beneficial effects of education on cognitive abilities, of approximately 1 to 5 IQ points for an additional year of education. Moderator analyses indicated that the effects persisted across the lifespan, and were present on all broad categories of cognitive ability studied. Education appears to be the most consistent, robust, and durable method yet to be identified for raising intelligence.
As you would expect from these two researchers, their analysis is highly detailed and sophisticated. They lay out the strengths and weaknesses of their three key approaches thus:
Each research design had its own strengths and weaknesses. The Control Prior Intelligence design produced precise, long-range estimates of the educational effect, and took into account the full range of educational variation. However, this approach did not employ a specific instrument for introducing differences in educational duration, and instead capitalized on naturally-occurring variation, which is itself multi-determined. Moreover, because the early and outcome tests were rarely identical (and because the early ability tests likely contained measurement error),the control for pre-existing ability levels was likely only partial.
The Policy Change design produced causal estimates across very large, population-based datasets. However, estimates from this approach were relatively imprecise, as is typical of instrumental variable analyses. Furthermore, because the policies used as instruments typically only increased educational duration for the subset of individuals who would have otherwise have attended school at the pre-existing minimum compulsory level, this design should be interpreted as producing a “Local Average Treatment Effect” that might not generalize across the full educational range(Morgan & Winship, 2015).
The School Age Cutoff design produced the largest number of estimates across a wide range of cognitive abilities, but was restricted to comparisons across adjacent school years. In this design, the critical causal estimate is based on comparing test scores in a given grade to a counterfactual formed by extrapolating within-grade age trends beyond the cutoff dates. This approach is powerful, but the key assumption—that the age trend extrapolates—is difficult to test. Moreover, although this approach produced notably large effect size estimates, we did not identify any School Age Cutoff studies that tested whether these effects persisted into adulthood. These estimates should thus be regarded with caution.
In three separate unconditional random-effects meta-analytic models (one for each study design), we estimated the effect of one additional year of education on cognitive outcomes. For all three study designs, there was a significant effect of one additional year of education. For Control Prior Intelligence, the effect was 1.197 IQ points (SE = 0.203, p= 3.84×10-09); for Policy Change, it was 2.056 IQ points (SE = 0.583, p= 4.23×10-04); and for School Age Cutoff, it was 5.229 IQ points (SE = 0.530, p= 6.33×10-23). An overall model including all estimates from all three designs found an average effect size of 3.394IQ points for one year of education (SE = 0.503, p= 1.55×10-11).
To my mind, the “Control Prior Intelligence” design is the best design, as the name suggests. It is the only one where the publication-bias funnel plot is funnel shaped. Yes, there is a confound (brighter kids may stay longer at school), but the error term feels much smaller than in the other two approaches. 1 IQ point gain seems credible, and it could be zero, if brighter students stay on for more education. My money is on Control Prior Intelligence as the best estimate of how much school boosts intelligence.
I would be more positive about the Policy Change results if there was a long-term follow-up. If extending years of schooling really works, Norweigians should be permanently brighter now by 2 to 4 IQ points (depending on how many extra school years) compared to when they had shorter, unreformed teaching. I doubt this, but data must decide the issue, not my surmises. There may not be a Hawthorne Effect (never was one) due to the extension of school years, but fake reforms of education may temporarily lift the morale of bored teachers, thus causing an upward blip in results which soon fades. Worth checking (and then if necessary doing another reform of some sort)!
As to School Age Cutoff, 5 IQ points per year is extraordinary. The authors are rightly cautious about this category. It would suggest that backwardness could be eradicated if slow learners were to be kept at school for another 3 years. I know that the authors do not make that assumption, but others will do so. If the data are correct, the policy implication stares us in the face.
The authors conclude:
The results reported here indicate strong, consistent evidence for effects of education on intelligence. Although the effects—on the order of a few IQ points for a year of education—might be considered small, at the societal level they are potentially of great consequence. A crucial next step will be to uncover the mechanisms of these educational effects on intelligence, in order to inform educational policy and practice.
These two papers strengthen the view that intelligence can be boosted, at least up till about age 18.
Education might be boosting intelligence. Even if not, I doubt it will be doing much harm, unless those who have tired of education are compelled to remain at school when there is work waiting for them, because work has intellectual demands to it, which should also, if these findings are correct, boost intelligence. (Worth testing to see if prior intelligence is boosted by a lifetime of supposedly cognitively demanding occupations). The authors refer to this general possibility as “downstream social processes”. It might also be prudent, in terms of boosting national intelligence, to prohibit retirement.
There is a case for education: whatever your abilities, you will have learned some skills and some facts. That is not to be sniffed at, even if you have learned nothing more than the correct way of sniffing snuff.