scholarly journals The Equal Environments Assumption in the Post-Genomic Age: Using Misclassified Twins to Estimate Bias in Heritability Models

2011 ◽  
Author(s):  
Dalton Conley ◽  
Emily Rauscher
Keyword(s):  
Equal Environments Assumption ◽  
Equal Environments

Twins: a test of the equal environments assumption

1990 ◽  
Vol 81 (4) ◽  
pp. 322-326 ◽  
Author(s):  
A. Morris-Yates ◽  
G. Andrews ◽  
P. Howie ◽  
S. Henderson
Keyword(s):  
Equal Environments Assumption ◽  
Equal Environments

scholarly journals Heritability and the Equal Environments Assumption: Evidence from Multiple Samples of Misclassified Twins

2013 ◽  
Vol 43 (5) ◽  
pp. 415-426 ◽  
Author(s):  
Dalton Conley ◽  
Emily Rauscher ◽  
Christopher Dawes ◽  
Patrik K. E. Magnusson ◽  
Mark L. Siegal
Keyword(s):  
Equal Environments Assumption ◽  
Multiple Samples ◽  
Equal Environments

Twin Studies of Political Behavior: Untenable Assumptions?

2008 ◽  
Vol 6 (4) ◽  
pp. 785-791 ◽  
Author(s):  
Jon Beckwith ◽  
Corey A. Morris
Keyword(s):  
Molecular Genetic ◽  
Genetic Research ◽  
Twin Studies ◽  
First Century ◽  
Behavioral Traits ◽  
Political Ideologies ◽  
Equal Environments Assumption ◽  
Twin Method ◽  
Genetic Techniques ◽  
Equal Environments

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 One important reason the twin method has been superseded is that it depends upon several questionable assumptions, the most significant of which is known as the equal environments assumption.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.

Can Comparison of MZ- and DZ-Twin Concordance Rates be Used Invariably to Estimate Heritability?

2007 ◽  
Vol 10 (5) ◽  
pp. 712-717 ◽  
Author(s):  
Peter V. Tishler ◽  
Vincent J. Carey
Keyword(s):  
Environmental Factors ◽  
Cigarette Smoking ◽  
Confidence Interval ◽  
Fixed Effects ◽  
Analytic Method ◽  
Comparison Model ◽  
Gender And Age ◽  
Equal Environments Assumption ◽  
Estimate Heritability ◽  
Equal Environments

AbstractProponents of the validity of the classical MZ-DZ twin comparison model for calculating heritability claim that the environments influencing MZ and DZ twin individuals are essentially identical. This ‘equal environments assumption’ may or may not be universally true when applied to the analysis of subjective traits. We examined the validity of this assumption as applied to the propensity for smoking cigarettes, reasoning that equality of environments should lead to equal smoking prevalences in MZ and DZ twin individuals. We identified 8 twin populations with data on smoking. We compiled odds ratios (ORs) for ever smoking in MZ and DZ twin individuals in these 8 studies and overall, using a fixed-effects meta-analytic method based on the Mantel-Haenszel procedure. The prevalence of smoking was less in MZ twin individuals than in DZ twin individuals in 7 of 8 studies. The overall OR was 0.86 (95% confidence interval 0.84, 0.89). ORs were virtually unchanged when the analyses were stratified for gender and age, and no differences were found in relation to the location of the study, the date of the study or the birth years of the cohorts. For cigarette smoking, the environments of MZ and DZ twins may not be co-equal. For subjective traits, heritability estimates may be influenced by these unequal environmental factors that differentially affect their development and characteristics in MZ and DZ twins.

scholarly journals Testing the Equal Environments Assumption in the Children of Twins Design

2010 ◽  
Vol 40 (4) ◽  
pp. 533-541 ◽  
Author(s):  
Laura B. Koenig ◽  
Theodore Jacob ◽  
Jon Randolph Haber ◽  
Hong Xian
Keyword(s):  
Children Of Twins ◽  
Equal Environments Assumption ◽  
Equal Environments
Sign in / Sign up

Export Citation Format

Share Document