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Twin Studies of Political Behavior: Untenable Assumptions?

Published online by Cambridge University Press:  13 November 2008

Jon Beckwith  and
Corey A. Morris
Jon Beckwith
Affiliation:
Department of Microbiology and Molecular Genetics, Harvard Medical School. E-mail: [email protected]
Corey A. Morris
Affiliation:
Program of Biological and Biomedical Sciences, Harvard Medical School. E-mail: [email protected]
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Abstract

Using the “classical twin method,” political scientists John Alford, Carolyn Funk, and John Hibbing conclude that political ideologies are significantly influenced by genetics, an assertion that has garnered considerable media attention. Researchers have long used human twins in attempts to assess the degree of genetic influence on various behavioral traits. Today, this methodology has been largely replaced in favor of contemporary molecular genetic techniques, and thus heritability studies have seen a diminishing role in behavioral genetic research of the twenty-first century. One important reason the twin method has been superseded is that it depends upon several questionable assumptions, the most significant of which is known as the equal environments assumption. Alford, Funk, and Hibbing argue that this crucial assumption, and thus their conclusion, holds up under empirical scrutiny. They point to several studies in support of this assumption. Here, we review the evidence presented and conclude that these attempts to test the equal environments assumption are weak, suffering significant methodological and inherent design flaws. Furthermore, much of the empirical evidence provided by these studies actually argues that, contrary to the interpretation, trait-relevant equal environments assumptions have been violated. We conclude that the equal environments assumption remains untenable, and as such, twin studies are an insufficient method for drawing meaningful conclusions regarding complex human behavior.

Type
Comment
Information
Perspectives on Politics , Volume 6 , Issue 4 , December 2008 , pp. 785 - 791
Copyright
Copyright © American Political Science Association 2008

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