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. 2015 Dec 28;113(4):1098–1103. doi: 10.1073/pnas.1508093112

Fig. 1.

Fig. 1.

Mild ID (lowest possible IQ stanine scale score of 1 equals lowest 3% IQ scores) is familial. Siblings of persons with mild ID have significantly and substantially lower IQs than the population. (A) Swedish results for male siblings of persons with IQ stanine score of 1 (mean = 3.31, SD = 1.80, n = 12,431 male pairs) and for the entire sibling population (mean = 5.10, SD = 1.95, n = 382,122 pairs). (B) Israeli results for male siblings of persons with IQ stanine score of 1 (mean = 3.36, SD = 2.46, n = 6,800 male pairs) and for the entire sibling population (mean = 5.49, SD = 1.94, n = 239,117 pairs). Note: individuals with severe ID are not included in the stanine IQ score distributions presented.