ERIC Number: EJ786696
Record Type: Journal
Publication Date: 2008
Reference Count: 0
A Twin-Family Study of General IQ
van Leeuwen, Marieke; van den Berg, Stephanie M.; Boomsma, Dorret I.
Learning and Individual Differences, v18 n1 p76-88 2008
In this paper we assess the presence of assortative mating, gene-environment interaction and the heritability of intelligence in childhood using a twin family design with twins, their siblings and parents from 112 families. We evaluate two competing hypotheses about the cause of assortative mating in intelligence: social homogamy and phenotypic assortment, and their implications for the heritability estimate of intelligence. The Raven Progressive Matrices test was used to assess general intelligence (IQ) and a persons IQ was estimated using a Rasch model. There was a substantial correlation between spouses for IQ (r = 0.33) and resemblance in identical twins was higher than in first-degree relatives (parents and offspring, fraternal twins and siblings). A model assuming phenotypic assortment fitted the data better than a model assuming social homogamy. The main influence on IQ variation was genetic. Controlled for scale unreliability, additive genetic effects accounted for 67% of the population variance. There was no evidence for cultural transmission between generations. The results suggested that an additional 9% of observed IQ test variation was due to gene-environment interaction, with environment being more important in children with a genetic predisposition for low intelligence.
Descriptors: Intelligence, Twins, Intelligence Quotient, Genetics, Interaction, Environmental Influences, Nature Nurture Controversy, Siblings, Parents, Heredity
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Publication Type: Journal Articles; Reports - Evaluative
Education Level: N/A
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