| Study | Sample | Head size measure | GMA measure | Correlation |
|---|---|---|---|---|
| Pearl (1906) | 935 German male soldiers | Perimeter | Officers' rating | 0.14 |
| Pearson (1906) | 2,398 British boys aged 3–20 years, standardized to age 12 | Length | Teachers' estimate | 0.14 |
| Pearson (1906) | 2,188 British girls aged 3–20 years, standardized to age 12 | Length | Teachers' estimate | 0.08 |
| Pearson (1906) | 1,011 British male university students | Length | Grades | 0.11 |
| Murdock & Sullivan (1923) | 291 American boys aged 6–17 years, standardized by age | Perimeter | Various IQ tests | 0.20 |
| Murdock & Sullivan (1923) | 395 American girls aged 6 to 17 years, standardized by age | Perimeter | Various IQ tests | 0.27 |
| Reid & Mulligan (1923) | 449 Scottish male medical students | Capacity | Grades | 0.08 |
| Sommerville (1924) | 105 White male university students | Capacity | Thorndike | 0.08 |
| Estabrooks (1928) | 172 White boys aged 7 years | Capacity | Binet IQ test | 0.23 |
| Estabrooks (1928) | 207 White girls aged 7 years | Capacity | Binet IQ test | 0.16 |
| Porteus (1937) | 200 White Australian children | Perimeter | Porteus Maze | 0.20 |
| Schreider (1968) | 80 adult Otomi Amerindians from Mexico | Perimeter | Form board | 0.39 |
| Schreider (1968) | 158 French farmers of unreported sex | Perimeter | Raven's Matrices | 0.23 |
| Klein, Freeman, Kagan, Yarborough, and Habicht (1972) | 172 Guatemalan Amerindian boys aged 3–6 years | Perimeter | Knowledge tests, with age standardized | 0.23 |
| Klein et al. (1972) | 170 Guatemalan Amerindian girls aged 3–6 years | Perimeter | Knowledge tests, with age standardized | 0.29 |
| Susanne & Sporcq (1973) | 2,071 Belgian male conscripts | Perimeter | Raven's Matrices | 0.19 |
| Weinberg, Dietz, Penick, and McAlister (1974) | 334 White boys aged 8–10 years | Perimeter | WISC | 0.35 |
| Passingham (1979) | 415 English villagers (212 men, 203 women) aged 18–75 years | Capacity | WAIS | 0.13 |
| Susanne (1979) | 2,071 Belgian male conscripts | Perimeter | Matrices | 0.19 |
| Pollitt, Mueller, and Liebel (1982) | 91 boys and girls aged 3–6 years | Perimeter | Stanford-Binet | 0.23 |
| Majluf (1983) | 120 boys and girls aged 8–20 months | Perimeter | Bayley motor development test | 0.35 |
| Ounsted, Moar, and Scott (1984) | 214 boys aged 4 years | Perimeter | Language test | 0.06 |
| Ounsted et al. (1984) | 167 girls aged 4 years | Perimeter | Language test | 0.07 |
| Henneberg, Budnik, Pezacka, and Puch (1985) | 151 Polish male medical students aged 18–30 years | Capacity | Baley's Polish language IQ test | 0.09 |
| Henneberg et al. (1985) | 151 Polish female medical students aged 18–30 years | Capacity | Baley's Polish language IQ test | 0.19 |
| Sen et al. (1986) | 150 16- to 18-year-old males in India | Perimeter | Raven's Matrices | 0.02 |
| Sen et al. (1986) | 150 16- to 18-year-old females in India | Perimeter | Raven's Matrices | 0.54 |
| Broman et al. (1987) | 18,907 Black boys and girls aged 7 years | Perimeter | WISC | 0.19 |
| Broman et al. (1987) | 17,241 White boys and girls aged 7 years | Perimeter | WISC | 0.24 |
| Ernhart, Marler, and Morrow-Tlucak (1987) | 257 3-year-old boys and girls | Perimeter | Stanford-Binet | 0.12 |
| Bogaert & Rushton (1989) | 216 White Canadian male and female university students, adjusted for sex | Perimeter | MAB | 0.14 |
| Lynn (1989) | 161 Irish boys aged 9–10 years | Perimeter | PMAT | 0.15 |
| Lynn (1989) | 149 Irish girls aged 9–10 years | Perimeter | PMAT | 0.23 |
| Lynn (1990) | 205 Irish children aged 9 years | Perimeter | Raven's Matrices | 0.26 |
| Lynn (1990) | 91 English children aged 9 years | Perimeter | Raven's Matrices | 0.26 |
| Osborne (1992) | 106 European-American boys aged 13–17 years; controls for height and weight | Capacity | Basic | 0.16 |
| Osborne (1992) | 84 African-American boys aged 13–17 years; controls for height and weight | Capacity | Basic | 0.34 |
| Osborne (1992) | 118 European-American girls aged 13–17 years; controls for height and weight | Capacity | Basic | 0.23 |
| Osborne (1992) | 168 African-American girls aged 13–17 years; controls for height and weight | Capacity | Basic | 0.13 |
| Rushton (1992b) | 73 East Asian-Canadian male and female university students | Perimeter | MAB | 0.14 |
| Rushton (1992b) | 211 White Canadian male and female university students | Perimeter | MAB | 0.21 |
| Lynn & Jindal (1993) | 100 9-year-old boys from northern India | Perimeter | Matrices | 0.14 |
| Lynn & Jindal (1993) | 100 9-year-old girls from northern India | Perimeter | Matrices | 0.25 |
| Reed & Jensen (1993) | 211 European-American male college students | Capacity | Raven's Matrices | 0.02 |
| Wickett et al. (1994) | 40 White Canadian female university students | Perimeter | MAB | 0.11 |
| Furlow, Armijo-Prewitt, Gangestad, and Thornhill, (1997) | 128 undergraduates, (60% female; 52% Caucasian, 38% Hispanic) | Perimeter | CFIT | 0.19 |
| Rushton (1997) | 100 East Asian-American 7-year-olds, 54% female | Perimeter | WISC | 0.21 |
| Tramo et al. (1998) | 20 individuals (10 pairs of identical twins) aged 24–43 years | Perimeter | WAIS-R | 0.14 |
| Tan et al. (1999) | 54 female university students in Turkey | Capacity | CFIT | 0.55 |
| Tan et al. (1999) | 49 male university students in Turkey | Capacity | CFIT | 0.29 |
| Ivanovic, Olivares, Castro, and Ivanovic (1996). | 4,124 school children of both sexes aged 6–17 years in Chile | Perimeter-for-age | School grades | 0.24 |
| Ivanovic, Forno, Castro, and Ivanovic (2000) | 4,509 5- to 22-year-old male and female students in Chile | Perimeter-for-age | Raven's Matrices | 0.22 |
| Wickett et al. (2000) | 68 individuals (34 pairs of brothers) aged 20–35 years | Perimeter | g, from MAB and other tests | 0.19 |
| Ivanovic et al. (2004) | 47 male 18-year-old high school students in Chile selected from the richest and poorest counties | Perimeter-for-age | WAIS-R | 0.50 |
| Ivanovic et al. (2004) | 49 female 18-year-old high school students in Chile selected from the richest and poorest counties | Perimeter-for-age | WAIS-R | 0.40 |
| Beckett et al. (2006) | 77 Romanian children (66% male) adopted into UK families with head size measured before age 43 months and GMA scores measured at 11 years | Perimeter | 4 scales from WISC-III (UK) | 0.27 |
| Bates (2007) | 164 university students aged 21 years (124 female, 40 male) | Perimeter | Raven's Matrices | 0.21 |
| Rushton, Cvorovic, et al. (2007) | 323 16- to 66-year-old Serbian Roma Gypsies (111 males, 212 females) | Capacity | Raven's Matrices | 0.13 |
| Rushton, Vernon, et al. (2007) | 239 18- to 25-year-old Canadians (108 males, 131 females; 77% White) | Perimeter | g, from MAB and Wonderlic | 0.19 |
| Number of samples: 59 | ||||
| Total N: 63,405 | ||||
| Unweighted mean r: 0.21 | ||||
| N-weighted mean r: 0.20 |
Note. CFIT, Culture-Free Intelligence Test; MAB, Multidimensional Aptitude Battery; NART, New Adult Reading Test; PMAT, Primary Mental Abilities Test; WAIS-R, Wechsler Adult Intelligence Scale-Revised; WISC, Wechsler Intelligence Scale for Children; WISC-III (UK), Wechsler Intelligence Scale for Children, 3rd Edition, UK standardization; Wonderlic, Wonderlic Personnel Test.