“Nature-Nurture and Intelligence”, 1935-08-01 (; similar):
“The present study approaches the problem by a comparison of two groups of children living in near-identical environments.” One group consists of adopted children and the other of “own” children. After surveying the records of 2449 children, 194 adopted children between the ages 5 and 14 (white, non-Jewish, north-European, and placed in their adoptive homes at the age of 6 months or younger) were matched with 194 own children whose sex was the same, whose age was within 6 months, whose fathers’ occupations belonged to the same group on the Minnesota Occupational Scale, whose fathers’ school attainments agreed within one school grade (mothers’ also), whose parents were white, non-Jewish, and north-European, and whose residence had been in communities of 1,000 or more. The children of both groups were given the Stanford-Binet and the Woodworth-Mathews Personal Data Sheet; the parents were given the Otis Self-Administering Test and the Stanford-Binet vocabulary.
“Variation in IQ is accounted for by variation in home environment to the extent of not more than 4%; 96% of the variation is accounted for by other factors… · Measurable environment does not shift the IQ by more than 3 to 5 points above or below the value it would have had under normal environmental conditions… · The nature or hereditary component in intelligence causes greater variation than does environment. When nature and nurture are operative, shifts in IQ as great as 20 points are observed with shifts in the cultural level of the home and neighborhood… · Variation in personality traits other than intelligence may be accounted for less by variation in heredity than by variation in environment.”
Earlier studies are reviewed and 8 references are cited.
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