I have always remembered the last line of Huckleberry Finn: “Aunt Sally she's going to adopt me and sivilize me, and I can't stand it. I been there before.”
Perhaps I share Huckleberry’s dislike of schools: “WELL, three or four months run along, and it was well into the winter now. I had been to school most all the time and could spell and read and write just a little, and could say the multiplication table up to six times seven is thirty-five, and I don't reckon I could ever get any further than that if I was to live forever. I don't take no stock in mathematics, anyway.”
However, I aim to be open to new ideas, and persons of great talent and learning assure me that going to school boosts IQ and that I should stop being churlish about such establishments.
Their arguments have to surmount a couple of hurdles. Firstly, “any fule kno” that the not so bright leave school early and the brighter ones stay on longer, so “years of schooling” is a dodgy measure which could show an apparent effect of schooling for artefactual reasons only.
Secondly, people understand that school might speed up some pedestrian mental processes, but leave you at the same intrinsic level of brightness at the end of schooling that you would have achieved anyway. 17/18 years of age is the proof of the pudding, when the final educated product rolls off the production line, possibly ready to make a useful contribution to society, so we should restrict ourselves to intelligence assessments conducted at around that age.
Thirdly, a body of work asserts that it does not matter whether children start school at 5 because they do just as well when they start at 7, but if schooling boosts IQ those who start at 7 should be duller, and that should show up for ever. The counter argument might be that school starting ages do not count, but school leaving ages do, but that would go against Abecedarian type results, which indicate that massive pre-school interventions with highly vulnerable children can boost IQ by 4 points which are sustained into middle age.
Fourthly, twin studies ought to show an effect of schooling on intelligence, but tend not to, which either suggests there isn’t any, or that current schooling is so similar that there is no school-based variance within standard educational systems.
What have the learned scholars arguing for the intelligence boosting effects of schooling got to offer?
The first helping is Ceci (1991) How Much Does Schooling Influence General Intelligence and Its Cognitive Components? A Reassessment of the Evidence. Developmental Psychology 1991, Vol. 27, No. 5, 703-722.
Ceci is also known for his work on racetrack experts (Ceci & Liker, 1986a, 1986b), research which has been often quoted as meaning that IQ does not count for much in real life. Doug Detterman demolished those papers so comprehensively that I am slightly on guard when reading this particular paper, but still reading it nonetheless. (It is silly and over-dramatic to avoid a person’s publications entirely because of some errors and contested results in other papers). Among the stronger studies he quotes Harnqvist's (1968) study of Swedish men. In 1961 Harnqvist selected a 10% random sample (approximately 12,000 men and women) of the Swedish school population who had been born in 1948 and who, at the age of 13, were given IQ tests. On reaching the age of 18 (in 1966), 4,616 of the Swedish men were tested as part of their country's national military registration. Thus, the study is not vulnerable to the usual sampling biases. Harnquist was able to compare children who were comparable on IQ, SES, and school grades at age 13 and determine the impact of dropping out of school on IQ at age 18. He found that for each year of secondary school (gymnasium) not completed, there was a loss of 1.8 IQ points—up to a maximum of nearly 8 IQ points difference between 2 boys who were similar in IQ, SES, and grades at age 13 but who subsequently differed in the amount of schooling completed by up to 4 years of high school. Naturally, one would need to look at the assumptions behind the SES and school grade “corrections” before being convinced by this, but this is strong stuff.
Ceci says: One of the best ways to document the impact of schooling on IQ is with a cohort-sequential analysis in which children of the same chronological age enter school at different times and remain there for similar lengths of time. By performing the appropriate statistical operations, it is possible to separate the effects of schooling from those of chronological age and, possibly; historical period, though the latter claim is a source of some contention.
Ceci summarises his paper’s findings thus: Taken together, the evidence for the influence of schooling on IQ appears to be fairly pervasive. Eight types of evidence for this relationship were reviewed: (a) the link between grade attained and IQ, (b) the impact of summer vacations, (c) the relationship between intermittent attendance and IQ, (d) the effect of late school onset, (e) the effect of early school termination, (f) the equivalence of aptitude and achievement test scores, (g) the
result of cohort-related changes, and (h) historical changes in the IQ-schooling link, all involving multiple replications. Although it is not possible to estimate with any confidence the precise decrement in IQ scores that befalls each month or year of missed or delayed school (Jencks et al., 1972, hazard the estimate of 1 IQ point decrement for each year of missed school), the trend is clearly one of declining IQ scores as a function of missed school. All of the studies that were reviewed accord with this statement, and only one empirical study argues otherwise.
Next up are Brincha and Gallowaya (2012) Schooling in adolescence raises IQ scores. PNAS www.pnas.org/cgi/doi/10.1073/pnas.1106077109
They say: Although some scholars maintain that education has little effect on intelligence quotient (IQ) scores, others claim that IQ scores are indeed malleable, primarily through intervention in early childhood. The causal effect of education on IQ at later ages is often difficult to uncover because analyses based on observational data are plagued by problems of reverse causation and self-selection into further education. We exploit a reform that increased compulsory schooling from 7 to 9 y in Norway in the 1960s to estimate the effect of education on IQ. We find that this schooling reform, which primarily affected education in the middle teenage years,
had a substantial effect on IQ scores measured at the age of 19 y.
This is a substantial paper, exploiting a natural experiment, in which various educational changes were made at different rates in different municipalities, all leading to an extra 2 years of school for adolescents, and a new unified middle school for those extra years. In Norway children begin school at 7, and this late start was maintained in the reformed system. There were no IQ measures beforehand. IQ was tested at age 19 when the men entered military service. So the paper is about men not women, and might be influenced by men’s slower maturation rates, and relates to the generation born between 1950 and 1958, and contains two important simultaneous changes: length and type of education. Given that there were no pre-school or early school IQ measures, the argument is based on various assumptions about what average IQs would have looked like if there had been no changes to the educational system.
As a consequence, the analysis of the results is quite complex. I am doing my best to simplify here. The first method, a difference-in-difference (DID) analysis, is to estimate the effect of the reform on the average IQ score for Norwegian men by comparing the change in IQ scores from the pre-reform period to post-reform period for municipalities that introduced the reform in a given year with the change in IQ scores in that same period in municipalities that did not introduce the reform in that particular year.
The second approach employs instrumental variables (IV) methods in which experiencing the new schooling system is used as an instrument for educational attainment (with appropriate controls for time trends and municipality of residence). The resulting system of two simultaneous equations is then estimated by two stage
least squares (2SLS). If we assume that the exclusive mechanism by which the reform affected IQ scores is by increasing the amount of schooling, the IV/2SLS approach allows us to break down the effect of the reform into (i) the effect of the reform on educational attainment and (ii) the effect of 1 y of additional schooling on IQ scores.
The results show that the educational reform (both length and type of education) increased men’s IQ by 0.6 points, which is statistically significant in this large population sample, though small of itself. I am favour plain statistics over the other more complicated analyses, because I am a primitive sort of person. For that reason, I went straight to the supplemental data.
Looking at Table S1 in the supplement it is clear that Norwegian men’s intelligence for all reasons including the educational reform rose for those of the 1950-1958 birth period from IQ 106 to 107.5. Given that this is a population sample we need to begin with an explanation as to why the initial score as not 100. Flynn effects probably account for this, in particular post-war recovery from Nazi occupation, but in fact the secular rise is said to have been faster in other periods. The IQ test produces stanine scores, so important detail is lost, though this should not be too important in this large sample. However, if during this birth period IQ rose by 1.6 IQ points, then the higher claimed rate which the authors show is the upward deviation from the trend line which the reform created for part of the test period.
The authors say: Because we estimate the total reform effect to be 0.6 IQ points and the total Flynn effect to be roughly 1.6 IQ points, we can attribute over one-third of the Flynn effect to the direct effect of the educational reform for the population of cohorts we study.
Having a sight of the IQs over a longer period would be a reality check as to whether there was an obvious and sustained upward movement in intelligence which could be attributed to the extra two years of schooling. Long data sets are the best, because all variations can be seen in historical context. If those historical data are available, they would be extremely informative. In the mean time, please give me a hand and have a look at the results section on pages 427 onwards to see what you make of them.
This is a good paper, highly detailed and open about the assumptions made. I need to look at the further analyses in more detail to see if I understand and agree with the higher gain estimates produced by them (of an enormous 3.7 IQ points per year), but if I have to summarise, I would put the gain at 0.6 IQ points.
It is hard to discuss any intelligence matter without making a bow towards the granite fortress of Edinburgh, and sure enough Stuart Ritchie, Timothy Bates, Geoff Der, John M. Starr, and Ian J. Deary have launched “Education is associated with higher later-life IQ scores, but not with faster cognitive processing speed”
Recent reports suggest a causal relationship between education and IQ, which has implications for cognitive development and ageing - education may improve cognitive reserve. In two longitudinal cohorts, we tested the association between education and lifetime cognitive change. We then tested whether education is linked to improved scores on processing speed variables such as Reaction Time, which are associated with both IQ and longevity. Controlling for childhood IQ score, we found that education was positively associated with IQ at ages 79 (Sample 1) and 70 (Sample 2), and more strongly for participants with lower initial IQ scores. Education, however, showed no significant association with processing speed, measured at ages 83 and 70. Increased education may enhance important later-life cognitive capacities, but does not appear to improve more fundamental aspects of cognitive processing.
In the LBC1921, each year of education was associated with a .66 IQ point advantage in IQ (95% confidence interval: .14 to 1.17 points) at age ~79, controlling for age 11 IQ, SES, age at both times of testing, and sex (Table 2, Step 3).
for individuals with lower scores on the initial IQ test, education was more strongly associated with higher later-life IQ.
This paper is particularly interesting because it has actual IQ results at age 11 and then uses exactly the same test decades later. By holding prior IQ constant it is in a position to show whether more education has an influence on later intelligence.
Correlation matrices for the two samples are shown above and below the diagonal, but are roughly the same. If we look at column 1 which relates to sample 1 then we can see that IQ at 11 is strongly related to later life IQ .66, to education .44, to age 11 social class .24 and more weakly to the reaction time and inspection time measures. Later life IQ shows the same sort of correlation with education .42 and stronger correlations with reaction time and inspection time.
The present results suggest that education has enduring effects on IQ test performance, even controlling for childhood IQ score, and that these effects are stronger for those with lower cognitive ability in childhood. However, they also suggest that these effects work via mechanisms – perhaps those involving improvements in specific skills - that are distinct from those generating differences in more fundamental measures of processing speed.
There is a slight problem with survivor bias in both samples: the participants are somewhat brighter than average, and in my view thus more likely to have stayed in education, which might somewhat inflate the apparent contribution of education. The first sample shows more variance in years of education than the second (2.47 vs 1.13) so in theory the effect of education should be greater in the first sample, but the second sample gains 15.24 points, the first 12.79 which is somewhat against prediction.
The paper is also interesting because it appears to reveal the nature and limitation of educational effects. It also shows greater gains for lower ability students, which would make sense if education had a mildly compensatory effect.
There is more in this next paper (working title: education and g) which is still under review and which is brought to you exclusively so that you can review it yourselves (thus spurring on the official reviewers):
Previous research indicates that education influences cognitive development, but it is unclear what, precisely, is being improved. Here, we tested whether education is associated with cognitive test score improvements via domain-general effects on general cognitive ability (g), or via domain-specific effects on particular cognitive skills. We conducted structural equation modeling on data from a large (n = 1,091), longitudinal sample, with a measure of intelligence at age 11 years and ten tests covering a diverse range of cognitive abilities taken at age 70. Results indicated that the association of education with improved cognitive test scores is not mediated by g, but consists of direct effects on specific cognitive skills. These results suggest a decoupling of educational gains from increases in general intellectual capacity.
The findings indicate that education’s ability to raise intelligence test scores (as shown by, e.g. Brinch & Galloway, 2012) is driven by domain-specific effects that do not show ‘far transfer’ to general cognitive ability. Such a result coheres with findings from Ritchie et al. (2013), who, in the same participants who were assessed here, showed no association of education with elementary cognitive measures such as reaction and inspection time, despite an association with improved scores on more verbal IQ subtests. Our results are also broadly consistent with recent reviews concluding that training programs targeting the specific skill of working memory can improve performance on working memory (and closely related) tasks, but this advantage does not seem to generalize to more distantly related skills such as reasoning and arithmetic (e.g. Melby-Lervåg & Hulme, 2012; though see Karbach & Verhaeghen, 2014). Finally, our results are in line with a study by Finn et al. (2014), who showed in a longitudinal sample of schoolchildren that while the quality of the school they attended had effects on tests of directly-taught subjects such as mathematics and English language, there was no relation of school quality to performance on tests of ‘fluid’ ability such as processing speed, working memory, and reasoning. These findings, along with the results of present study, point to a conceptualization of education as a training program that develops particular intellectual abilities but not more fundamental capacities such as the efficiency of cognitive operations.
In summary, it very much looks like more years of education are associated with an increase in intelligence test scores, but not anything like as strongly to underlying general intelligence or to underlying basic processing speeds. There is some hesitancy on my part, because I need to look at the arguments and the statistical techniques in more detail, but the Lothian cohorts get round most of those problems, simply because they have IQ measures at age 11.
So, where does all this leave our hero? Huckleberry did admit: “At first I hated the school, but by and by I got so I could stand it.” Perhaps it boosted his IQ, though not his processing speed. I hope it did not stop him from drifting down the Mississippi on those sunny afternoons I still remember.