Abstract
We examine updated Wechsler IQ data in 7-year old twins from the Louisville Twin Study for evidence of an interaction between the heritability of IQ and socioeconomic status. Data records that had never been entered were recovered, allowing us to increase previously reported sample sizes by more than 20 %. Twin families were assigned socioeconomic status scores using a Hollingshead index based on parental education and occupation. A structural equation model in which genetic and environmental variances were modeled as squared linear functions of SES provided ambiguous replication of earlier findings from the National Collaborative Perinatal Project: relations between SES and heritability for performance and full scale IQ were in the same direction as the previous report, but at p < 0.07. As was the case in Turkheimer et al. (Psychol Sci 14(6):623–628, 2003), no interaction was found for VIQ. These results cannot yet be taken as a definitive replication of Turkheimer et al. (Psychol Sci 14(6):623–628, 2003). Many more measurement occasions, subtests and environmental moderators remain to be analyzed.
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Acknowledgments
This work was supported by grants 1R03AG048850-01, T32AG020500, T32AG000037-37, F31AG044047-01A1 from the National Institute of Aging.
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Eric Turkheimer, Christopher E. Beam and Deborah W. Davis declare that they have no conflict of interest.
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The secondary data analysis reported here was approved by the Institutional Review Board for the Social and Behavioral Sciences at the University of Virginia. All procedures followed in the secondary data analysis reported here were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). Informed consent was obtained from all patients for being included in the study.
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Turkheimer, E., Beam, C.E. & Davis, D.W. The Scarr-Rowe Interaction in Complete Seven-Year WISC Data from the Louisville Twin Study: Preliminary Report. Behav Genet 45, 635–639 (2015). https://doi.org/10.1007/s10519-015-9760-4
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DOI: https://doi.org/10.1007/s10519-015-9760-4