Table 3.

Estimates of Genetic and Environmental Variance Components in General Intelligence and Educational Attainment at Three Levels of General Intelligence in Sweden and Minnesota

Variance component	Sweden			Minnesota
	−2 SD	0 SD	2 SD	−2 SD	0 SD	2 SD
General intelligence
Genetic	same	0.58 (0.53, 0.64)	same	same	0.73 (0.58, 0.85)	same
Shared environmental	same	0.26 (0.20, 0.32)	same	same	0.07 (0.00, 0.22)	same
Nonshared environmental	same	0.16 (0.15, 0.18)	same	same	0.20 (0.17, 0.22)	same
Educational attainment
Genetic	0.31 (0.17, 0.50)	0.50 (0.42, 0.58)	0.73 (0.50, 1.002)	0.16 (0.09, 0.26)	0.35 (0.13, 0.61)	0.64 (0.09, 1.57)
Shared environmental	0.13 (0.03, 0.55)	0.25 (0.19, 0.34)	0.42 (0.22, 0.68)	0.96 (0.79, 1.13)	0.39 (0.14, 0.61)	0.07 (0.00, 0.68)
Nonshared environmental	0.21 (0.16, 0.23)	0.25 (0.23, 0.27)	0.29 (0.23, 0.35)	Same	0.26 (0.22, 0.31)	same

Note: The table presents estimates of the variance in general intelligence and educational attainment explained by genetic, shared environmental, and nonshared environmental influences. Estimates are presented for three levels of general intelligence: the mean, 2 standard deviations below the mean, and 2 standards above the mean; “same” indicates that there is no difference from the variance at the mean level. The variance components are raw and do not necessarily add up to 1.00. Numbers in parentheses are 95% confidence intervals. The Swedish data included only male pairs. The Minnesotan data included both male and female same-sex pairs. In Sweden, general intelligence was measured by g factor score at age 18, and educational attainment was assessed through 2004. In Minnesota, intelligence was measured by IQ score at age 17, and educational attainment was assessed at age 24.