Raven’s Progressive Matrices

Brain size

Evolutionary Explainations



-I.Q of an adult male 3.1 to 5.1 points higher (δ male-female 0.25 to 0.34SD).

-Faster development for women, but peaks earlier (parallel to physical growth).

-I.Q of men becomes superior at about 16 years.

-Size of the brain of adult men bigger by 110 to 150 cubic cm (δ = 0.57 SD).

-19.3 billion neurons in women, 22.8 billion neurons in men.

-Highest cortical thickness in men (δ = 0.28SD)

-Men also have quicker Reaction Time (Deary, 2006 Ritchie, 2018), a consequence of the positive correlation between I.Q and reaction time.

Fig. 1. Total sample male and female general intelligence g (HFA/S–L, see text) distributions and male–female ratio as a function of male g = .23 (SD = 1.03) and female g = .23 (SD = .93). Nmales = 90 (mean age 13.0, SD = 3.54) and Nfemales = 91 (mean age 12.8, SD = 3.6).

In Detail

The brain size of adult men is about 110 cc (0.78 SD) larger. The IQ-brain size correlation is +0.44, so the theoretical male superiority in adulthood is (0.78×0.44) = 0.35SD, ie in IQ points: (0.35×15) = 5.1 IQ points, exactly what is found empirically in the tests.


A problem that has sometimes been raised as part of the positive relationship between brain size and intelligence is that women have smaller brains than men and yet it has been virtually universally claimed that there was no differences of intelligence between men and women.
For example, “women’s brains are 10% smaller than men’s, but their IQ is on average the same” (Butterworth 1999: 293). Since women with a smaller brain size would be as smart as men, it appears that brain size has no effect on intelligence. This is the conclusion drawn by Gould (1996, p.132), who writes that he refutes “the myth that differences in brain size would have a relationship to intelligence” The smaller average size of women’s brains has been demonstrated by Ankney (1992) and Rushton (1992). Ankney has calculated that the average men’s brain, adjusted for body size, is 100 grams heavier. Rushton calculated from another set of data from 6325 military men that the brain average, adjusted for body size, is 1442cc for men and 1332cc for women, a male advantage of 110cc; 1CC of brain tissue weighs about 1 gram, so that the results of Ankney and Rushton are very similar.

So we have a paradox: the size of the brain is positively related to intelligence, men have on average a larger brain, and yet men and women would have the same intelligence.
Richard Lynn presented the resolution of this paradox in Lynn (1994 and 1999) and in Lynn and Irwing (2004).

Up to the age of 15 years, males and females have approximately the same intelligence, except for a small male advantage on the visualization abilities; however, from the age of 16 years, males begin to show greater intelligence, reaching an advantage of from three to five IQ points in adults. This has been further confirmed by Paul Irwing and myself (Irwing & Lynn, 2005; Irwing, 2012), by Victoria Bourne, Helen Fox, Ian Deary, and Lawrence Whalley (2007).

This advantage is fully explicable by the larger size of mens’ brain. Men and women experience the same environment and therefore environmental factors can not account for the difference between men and women. The evolutionary  explanation of the average slightly higher intelligence of men is that men compete with each other to obtain women and in the evolution of hominids, the intelligence played an important role. Women do not compete for men.

Coming to corroborate male intellectual advantage, Deary has shown that men have a faster reaction time (RT) than women. This is a consequence of the positive correlation between simple reaction times and Q.I.

A new study (2019) on 10,300 Spaniards again confirmed the difference in speed of development between the sexes, with a small male cognitive advantage in adulthood.

In adulthood, men’s I.Q is on average slightly higher (4-5 I.Q points).

Below, summary of sex differences found at the national level. A minus sign indicates a female advantage (only in Argentina). For all studies, the male intellectual advantage is 0.206SD, ie 3.1 points of Q.I.

Summary on Sex Differences in Intelligence by Richard Lynn (2017).

Click to enlarge



WAIS Full Scale IQ

All 42 studies show a male advantage, median +0.24sd or 4 IQ points

Table 5.5. Sex differences on the WAIS Full Scale IQ and Performance subtests; (ds; positive signs denote males score higher)

Country Test: N FS  IQ Reference 
Brazil WAIS-III: 3494 .07 Victora et al., 2015 
Canada WAIS-III: 1104 .11 Longman et al., 2007 
Chile WAIS-IV: 887 .20 Diaz & Lynn, 2016 
China WAIS-R:1406 .24 Dai et al., 1991 
China WAIS-R:1979 .33 Lynn & Dai, 1993 
China WAIS-R:120 .43 Yao et al., 2004 
China WAIS-111:888 .29 Chen & Lynn , 2020c 
China WAIS IV:311 .62 Gao et al., 2015 
Canada WAIS 111:1104 .11 Longman et al., 2007 
Denmark WAIS:62 .21 Nyborg, 2005 
Germany WAIS-IV:1425 .21 Daseking et al., 2017 
Italy  WAIS-R:1168 .45 Tommasi et al., 2015 
Japan WAIS-R:1402 .22 Hattori & Lynn, 1997 
Netherlands WAIS:2100 .27 Stinissen, 1977 
Netherlands WAIS 111:522 .24 Van der Sluis et al, 2006 
Romania  WAIS:100 .44 Dumitrascu, 1999 
Romania: Roma  WAIS:100 .44 Dumitrascu, 1999 
Russia WAIS:296 .13 Grigoriev et al, 2016 
Russia WAIS:1800 .22 Grigoriev et al, 2016 
Scotland WAIS-R:200 .39 Lynn, 1998 
South Korea  WAIS-IV:1228 .31 Lynn  & Hur, 2016 
Spain WAIS 111:1369 .24 Colom et al., 2002 
Sudan WAIS-R:330 .31 Sulman et al, 2018  
Sudan WAIS-R:319 .21 Sulman et al, 2018  
Taiwan WAIS 111:888 .29 Chen & Lynn, 2021a 
Taiwan WAIS 1V:1105 .35 Chen & Lynn, 2018 
United States W-Bell:235 .59 Strange & Palmer, 1953 
United States W-Bell:153 .20 Norman, 1953 
United States W-Bell:392 .29 Goolishian  & Foster, 1954 
United States WAIS:1700 .10 Matarazzo, 1972 
United States WAIS:279 .40 Boor, 1975 
United States WAIS:588 .17 Horn et al., 1979 
United States WAIS:521 .13 Turner & Willerman, 1977 
United States WAIS:649 .09 Doppelt & Wallace, 1955 
United States WAIS:649 .09 Doppelt & Wallace, 1955 
United States WAIS:100 .33 Shaw, 1965 
United States WAIS-R:230 .27 Arceneaux et al., 1996 
United States WAIS-R:206 .28 Ilai & Willerman, 1989 
United States WAIS-R:1880 .15 Matarazzo et al., 1986 
United States WAIS-III: 2450 .18 Irwing, 2912 
United States WAIS IV:2200 .15 Piffer, 2016 
United States WAIS 111: 850 .04 Du Pont et al., 2020 
Median   .24  

WAIS Full Scale IQ

32 studies on 33 show a male advantage, median +0.3 (4.5 IQ points)

Table 4.3. Sex differences (ds) for the Standard and Advanced Progressive Matrices in general population samples aged 20-80 years. Minus signs denote higher means obtained by females.

Country N:MN:FdReference
Britain 300240 .29Heron & Chown, 1967 
Hungary 250250 .17Szegedi, 1974 
Israel 100100 .31Guttman, 1974. 
Hawaii 939971 .37Wilson et al., 1975 
Taiwan 225 225 1.33Adair & Pollitt, 1985  
Belgium 850979 .31Deltour, 1993 
Belgium 101174 .38Deltour, 1993 
USA 63  80 .16Sitkei & Michael, 1996 
Belgium ** 564802 .21Dufouil et al., 1997 
Brazil 1921741 .28Campos, 1999 
USA** 92114 .31Salthouse, 2001 
Scotland 210217 .11Deary et al., 2004 
Scotland 230313 .29Deary et al., 2004 
Guatemala 683786 .52Martorell et al., 2005  
Brazil** 104265 .49Rossetti et al., 2009  
Pakistan 9971019 .04Ahmad et al., 2008  
Morocco  92110 .38Sellami et al., 2010  
Spain  101157 .15Diaz et al., 2010.  
Sudan 115125 .12Khaleefa et al., 2010 
N. Zealand 143187 .22Fletcher & Hattie, 2011 
Argentina  374390 -.02Flynn, 2012 
Libya 300300 .37Al-Shahomee, 2012 
Libya 260260 .36Al-Shahomee & Lynn, 2012 
Brazil** 454534 .10Flores-Mendoza et al., 2013 
Brazil**  161386 .65Braga et al., 2014 
Serbia 6274 .27Čvorović & Lynn, 2014 
Romania* 618823 .18Iliescu et al., 2016 
Australia**   128327 .30Waschl et al, 2016  
Brazil**  381216 .43Flores-Mendoza et al., 2016 
USA*** 393503 .21Van der Linden et al., 2017 
Poland** 218218 .12Gignac & Zajenkowski, 2019 
USA*** 346399 .05Du Pont et al., 2020  
Portugal 250272 .34Queiro-Garcia et al., 2021 
Median – .30 –

 *Progressive Matrices Plus; **Advanced Progressive Matrices; *** Advanced Progressive Matrices Short Form 

References for the whole page

“Race differences in intelligence. An evolutionary Analysis“, Chapiter 16, Richard Lynn, Washington Summit Publisher 2nd edition 2015.

 “Age and sex differences in reaction time in adulthood, results from the United Kingdom health and lifestyle survey”, Psychology and aging (2006), Ian J. Deary.

Van Der Linden D., Curtis S.D. et Madison G. (2017) “Sex differences in brain size and general intelligence (g)”, Intelligence.

Lynn R., Irwing P. (2006) “Intelligence: Is there a sex difference in IQ scores ?” Nature 442, E1, doi:10.1038/nature04966.

Arribas D., Aguilaa F. et al. (2019) “Testing the developmental theory of sex differences in intelligence using latent modeling: Evidence from the TEA Ability Battery (BAT-7)”

Lynn R. (2017) Sex Differences in Intelligence. Reply to Comments. Mankind Quarterly 58:1145-156.