Wednesday, 19 November 2014

Male versus female IQ in a pioneering study from 1923


Pioneering studies of IQ by G.H. Thomson and J.F. Duff – An example of established knowledge subsequently ‘hidden in plain sight’ Bruce G. Charlton. Medical Hypotheses. 2008; 71: 625-628.


Perhaps the earliest authoritative measurement of a social class gradient in IQ, with a stratification of occupations among the parents of children with different IQs, is seen in two fascinating papers published in 1923 and 1929 in the British Journal of Psychology. The authors were GH Thomson and JF Duff (both of whom were later knighted) and the papers’ main findings were confirmed by later researchers. Results of an intelligence test administered to 13419 children aged 11–12 were analyzed according to parent’s occupation. The average children’s IQ at extremes of social class among their parents included clergymen-121, teachers-116 and bankers and managers-112 at the upper end; while at the lower end there were ‘cripples and invalids’-94, cattlemen-93, hawkers and chimneysweeps-91, and the ‘insane, criminal’-88. More than 100 specific categories of parental occupations were then combined into 13 social classes, with their children’s average IQ as follows: Professional-112; Managers-110; Higher Commercial-109; Army, Navy, Police, Postmen-106; Shopkeeping-105; Engineers [ie. apprenticed craftsmen, such as mining engineers]-103; Foremen-103; Building trades-102; Metal workers, shipbuilders-101; Miscellaneous industrial workers-101; Miners and quarrymen-98; Agriculture-98; Labourers-96. A follow-up study compared an ‘intelligent’ group (IQ 136 plus) with a matched IQ 95–105 ‘control’ group. IQ testing at age 11–12 was predictive of teacher’s reports of higher levels of intelligence and health at age 16; and better performance in official examinations. The occupations of fathers, grandfathers and uncles were consistent with occupation being indicative of ‘an inherited quality’ (i.e. IQ) and there was regression from parents to grandparents and uncles among the ’intelligent’ but not among controls. Other findings included a wider variance in intelligence among boys than girls, and descriptions of the predictive value of IQ in estimating future education, examinations and health. Although the distribution, heredity and predictive value of childhood IQ measurements was once quite widely understood, for the last few decades IQ research has been regarded as morally-suspect and IQ scientists subjected to vilification, persecution and sanctions. Ignorance and misunderstanding of IQ is the norm among intellectual elites in schools, universities, the media, politics and public administration. Consequently IQ research is actively-shunned, and has near-zero influence on public policies. Since this area of science has been so comprehensively ‘disappeared’ from public consciousness as a result of socio-political pressure; it seems probable that other similarly solid and vital domains of scientific knowledge may also be ‘hidden in plain sight’.


The 1923 Duff and Thomson study began when an intelligence test was administered on February 24 1922, to all children aged 11 and 12 at state elementary schools in Northumberland excluding Newcastle and Tynemouth; yielding an enormous sample of 13419 children (6930 boys; 6695 girls)...

Average IQ was 99.6, 877 children had an IQ of 120 plus and 1337 had an IQ less than 80.

Boys exhibited a slightly larger apparent standard deviation than girls (no specific numbers were given by the authors), with a greater proportion of the most intelligent children being boys (IQ 130-9 - 80 boys, 49 girls; IQ above 140 – 12 boys, 4 girls) and also a greater proportion of the least intelligent being boys (IQ below 80 – 715 boys, 622 girls).

NOTE added - No information was given on how the IQ was calculated; but it is likely that it was the old ratio system, so that an IQ of 140 at age 11 is generated by the child of 11.5 years old scoring at approx. the level of the average 16 year old (i.e. 16/11.5 = approx. 1.4 or an IQ of 140).

It has since been almost universally confirmed that there is a higher proportion of boys and men in the highest IQ and lowest IQ levels.

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  1. There is nothing new under the sun, it seems.

  2. No this is all wrong! People from lower socioeconomic classes are not less intelligent, they are just...suppressed and disadvantaged, or something. Don't you follow advances in Scientific understanding in the 'newspapers'?! As long as we structure our society to model this newly discovered 'truth' everything will be just fine.

  3. The PC virus is stronger than ever. As an existentialist this is the only thing to make me wonder about dark forces.