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Does the world need another IQ test? There are many well-validated tests, and also a number of short tests suitable for large scale surveys, many of which take less than 10 minutes, and several useful ones which take less than 5 minutes. However, if you are searching for a good measure of the manifold panoply of human achievement, it might be worth spreading the net even wider, so as to capture every gem of intellectual prowess. In that case, who would sit through such an assessment, given that the gold standard Wechsler tests take more than an hour?

One approach, in which the Madrid team under Roberto Colom have been prominent, is to cast the assessment in the form of a computer game. This makes it accessible to a much wider audience, and increases the number of wider-ranging intelligence test which can be used as part of genetic studies of intelligence. In fact, the “gamification” is rather light, a surface gloss only, but it seems to have been enough.

Now Robert Plomin’s team have added further to their own already published game-based intelligence test, and have interesting new results to report. The author’s names are a good roll-call of the new wave of intelligence researchers.

They point out that genome-wide association studies haven’t yet explained as much variance as can be obtained from twin studies. Critics have called this “missing heritability”, which misses the point. We know from twin studies that intelligence is heritable, and genome-wide association studies are trying to identify the genes responsible for this result. (We know that genetics is powerful in real life, now we need to show it in theory). Part of the problem is that larger studies have put together results from disparate tests, so the team has designed a 40 item intelligence game which produces a reliable (internal consistency = .78, two week retest reliability = .88) measure of g which they have given to 4,751 young adults from their twin study.

This novel g measure, which also yields reliable verbal and nonverbal scores, correlated substantially with standard measures of g collected at previous ages (r ranging from .42 at age 7 to .57 at age 16). Pathfinder showed substantial twin heritability (.57, 95% CIs = .43, .68) and SNP heritability (.37, 95% CIs = .04, .70). A polygenic score computed from GWA studies of five cognitive and educational traits accounted for 12% of the variation in g, the strongest DNA-based prediction of g to date. Widespread use of this engaging new measure will advance research not only in genomics but throughout the biological, medical, and behavioural sciences.

So, they have verbal and nonverbal scores, and can generate a gene-based prediction which accounts for 12% of intelligence variance, a good result by current standards. The test used item response theory to select the most powerful items, and get maximum predictive power from the fewest number of items.

The software is free, and if it gets taken up by further genome wide association studies then the variance accounted for may rise from 12% to 30%, assuming that the heterogeneity of test is a complicating factor which universal use of this test would overcome. The great advantage of a polygenic risk score for intelligence is that you can get a prediction from birth onwards, which overcomes the problem that early tests of intelligence do not get reliable till about age 11, and gain in accuracy thereafter. Early predictions might be a more precise way of evaluating whether early teaching has any effect on later intelligence.

To my eye the missing letter test doesn’t seem worth including. Sure, it is a basic process measure, but a bit out on a limb in factorial terms.

This very big sample of 4,751 25-year-olds shows significant sex differences in favour of men. The authors don’t comment on this, but it fits the emerging pattern of a male intellectual advantage in adulthood.

They say:

Heritability was 57%, shared environmental influence was 8% and multivariate polygenic scores predicted up to 12% of the variance. The latter finding –that 12% of the variance of Pathfinder g can be predicted by DNA –makes this the strongest polygenic score predictor of g reported to date. Although 12% is only one fifth of the twin study estimate of heritability, we hope that adding Pathfinder g in large biobanks will improve the yield of 21meta-analytic GWAS analyses by increasing sample sizes and decreasing heterogeneity of cognitive measures. It should be possible to use the brute force method of increasing sample sizes, especially with less heterogeneity of measures, to close the missing heritability gap from 12% to the SNP heritability of about 30%.

Getting above 30% of the variance will be hard, to reach the 60% heritability revealed by twin studies. That will require whole genome sequencing.

The summary is that the team have created a good new 15-minute IQ test which correlates well with the many longer assessments used over the years on their very large sample of twins. It also has good predictive power. If more widely adopted, and the few bits of explanatory English language translated into other languages, it could be a very useful contribution to large GWAS investigation of the genetic basis of intelligence.

You can get Pathfinder here:

• Category: Science • Tags: IQ 
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  1. anon[321] • Disclaimer says:

    A couple of thoughts:

    – I have a vague idea that the correlation of one IQ test with another should usually be around 0.8. The correlation of 0.57 here looks lower than that. How significant is this?

    – It’s great that the test is reliable. How much of a training effect does it have? (I have, again, a vague idea that Raven’s Progressive Matrices don’t do well at assessing subjects who have been trained for the assessment.) I notice that the website consists only of “email us and tell us about your research, and we may let you see the test”. I infer that some sort of risk is perceived from letting the test get out into the public. I was kind of hoping to take it, but it looks like that must not be allowed.

    • Replies: @James Thompson
  2. res says:

    Is it reasonable to interpret Figure 3A as indicating Pathfinder has a ceiling of around +2.5 SD?

    Supplementary Table 11 has the numbers underlying the sex differences graphic. It also adds percent variance explained by sex which is less than or equal to 3% for all of the tests and composites.

    I really wish someone would do a large scale IQ GWAS which included CNVs (Copy Number Variants).

    P.S. Here is a Cohen’s d calculator based on group means and SDs. Just square their r to get r^2 (which is 0.0225 for g).

    • Replies: @James Thompson
  3. ruralguy says:

    This science seems to have not kept up with advances in the field of mathematics. “g” in mathematics is a scalar. To map the composite cognitive and memory functions to a scalar requires a lucid and rigorous understanding of this mathematical map. In mathematical control theory, this type of characterization has been done through several means. In the earliest stage of control theory, a black-box functional behavior is determine by subjecting it to various impulses at different frequencies. The impulse response then determines the black-box system characteristic. Of course, this doesn’t apply to human cognitive functions. Around the 1960s, control theory started characterizing unknown blackboxes, by analyzing the inputs and output spaces of the black box. A model of the internal behavior of the box can be derived solely from these inputs and outputs, if the system meets “realizeable” criteria. This might better characterize the human cognitive functions, rather than just a scalar with no rigorous map to the black box functions. Finally, control theory had progressed even further to characterize “complex” black boxes through the mathematics of complex systems theory. For example, a random properties of these complex systems are analyzed with random matrix theory, while non-random aspects can be characerized by network formations, cooperative/non-cooperative game and game/evolutionary theory. Like a chess game, the brain likely has complex dynamics that are best expressed in the PDEs of evolutionary game theory. Like a chess game, the tactics and strategies of one palyer’s pieces depend on how cooperatively the pieces are used.

  4. Anonymous[145] • Disclaimer says:

    Have you seen this study?

    There are panicked headlines appearing all over the place. From a quick read, a few things leapt out at me:

    The population was unusually well-educated. Of 673 mothers, 262 had graduate degrees. Only 111 had a high school degree or less.

    Small sample size.

    Perhaps the most consequential: the researchers write: One aspect also not investigated here is the impact of mask-wearing by the study staff during child visits and assessments [53]. The inability of infants to see full facial expressions may have eliminated non-verbal cues, muffled instructions, or otherwise altered the understanding of the test questions and instructions.

    Gee. Ya think? (/sarcasm)

    I rather think testing under those circumstances would suppress anyone’s score on an IQ test.

  5. @anon

    It would be better if this test correlated more strongly with the other tests given to the subjects in this study, but there are two issues here. 1) Many of the tests were given when the children were young, and their own scores on those tests won’t correlate perfectly with their eventual adult scores. 2) This is a short test, and there is always a price to be paid for brevity.

    Yes, the authors have to protect the integrity of the test, so they want to keep for researchers. I should have stated that.

  6. dearieme says:

    I’ve got through life having taken IQ tests only twice. I dare say many people have never taken a test. Can you give any guidance on that, doc, however rough and ready?

    • Replies: @James Thompson
  7. dearieme says:

    Talking of brains and genetics I’ve just seen these two surprising facts.

    (i) no congenitally blind person ever gets schizophrenia,

    (ii) congenitally blind people are about fifty times more likely to get autism than everyone else.

    There are more things in heaven and earth …

    • Thanks: Right_On
    • Replies: @Right_On
  8. @res

    Hadn’t noticed the ceiling. Perhaps +2.75 but not the full 3 sigma.

    Sex diff is a massive 4.65 IQ points which seems extreme. I notice it is mostly a female group, which may have messed things up. Perhaps duller guys didn’t bother to participate.

  9. @dearieme

    Group tests far more likely than detailed face to face examinations, but I don’t have a handle on how many are give now. The Cognitive Assessement Test (computer administered in schools) is probably the most likely that students would take now.

    • Thanks: dearieme
  10. You can get Pathfinder here:

    No. You cannot get Pathfinder there. You get some nonsense that says: email us.

    About your study.

    I don’t have a study.

    Where is Pathfinder? Could you try again to be accurate?


    • Replies: @James Thompson
  11. Right_On says:

    Mind-blowing – if you’ll pardon the expression.

    Wonder what New Left psychiatrist R. D. Laing would have said to try to explain that.

  12. says:

    A rare source of Spatial IQ data. The US Army IQ results derived from the Project Talent sub-component data that include Spatial IQ components. It is obvious that the Army report avoided using the words IQ and used the metric of the proportion of a selected group which inherently they are the same. There are differences from the NLS data, dispite the whinges that Spatial IQ was not used in the NLS results, the inclusion of Spatial IQ component only marginally improved the STEM major scores and not enough to compete with that for the Business major. The IQvm that involved only the verbal and maths components was reported to mimic SAT score, i.e. biased against maths score which has low ceiling score and that might explain why the STEM scores are so terribly low. Significant number of “Housewives” (50%) surprisingly have very high Spatial IQ. That may have confirmed the suggestion that males mostly navigate by “direction”, a 1D efforts, whereas females mostly navigate by landmarks, i.e. 3D efforts. From the results it is apparent that the inclusion of Spatial IQ downgrades the scores for the Humanities and Arts majors and so it is most probably politically non-viable. There are also reports that Spatial IQ is trainable, like playing Tetris, and so it might be subjected to people gaming the system.


    Transformed to IQ,

    The procedure for the IQ transformation so happen to be exactly the same (Migrant Average Group IQ, MAGIQ) that I used for predicting the average group IQ of selected migrants, the average group IQ of the specifically selected from another more general selected group, and it involves using truncated normal distributions. I thought the precedure is very obvious but there are people asking about it. I might describe it when I have more free time.

  13. @restless94110

    Sorry. It is available free to researchers, not for general use by individuals.

    • Thanks: restless94110
  14. So, in a nutshell, the apple doesn’t fall far from the tree. Who the hell doesn’t know that? So many words from grifters who make a fortune with their sheer ‘brilliance’, horseshit research and empty rhetoric. I remain unimpressed. Anyone with a brain does.

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