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

Dalton Conley, Emily Rauscher

NBER Working Paper No. 16711
Issued in January 2011
NBER Program(s):Children, Economics of Education, Health Economics

While it has long been known that genetic-environmental covariance is likely to be non-trivial and confound estimates of narrow-sense (additive) heritability for social and behavioral outcomes, there has not been an effective way to address this concern. Indeed, in a classic paper, Goldberger (1979) shows that by varying assumptions of the GE-covariance, a researcher can drive the estimated heritability of an outcome, such as IQ, down to zero or up close to one. Survey questions that attempt to measure directly the extent to which more genetically similar kin (such as monozygotic twins) also share more similar environmental conditions than, say, dizygotic twins, represent poor attempts to gauge a very complex underlying phenomenon of GE-covariance. Methods that rely on concordance between interviewer classification and self-report offer similar concerns about validity. In the present study, we take advantage of a natural experiment to address this issue from another angle: Misclassification of twin zygosity in a nationally-representative study (Add Health). Since such twins were reared under one "environmental regime of similarity" while genetically belonging to another group, this reverses the typical GE-covariance and allows us bounded estimates of heritability for a range of outcomes of interest to medical and behavioral scientists.

download in pdf format
   (143 K)

email paper

Machine-readable bibliographic record - MARC, RIS, BibTeX

Document Object Identifier (DOI): 10.3386/w16711

Published: Conley, D., Rauscher, E., Dawes, C., Magnusson, P. K., & Siegal, M. L. 2013. “Heritability and the Equal Environments Assumption: Evidence from Multiple Samples of Misclassified Twins.” Behavior Genetics . 43:415-426.

Users who downloaded this paper also downloaded* these:
Conley and Rauscher w16026 Genetic Interactions with Prenatal Social Environment: Effects on Academic and Behavioral Outcomes
Oreopoulos, Stabile, Walld, and Roos w11998 Short, Medium, and Long Term Consequences of Poor Infant Health: An Analysis using Siblings and Twins
Lochner w16722 Non-Production Benefits of Education: Crime, Health, and Good Citizenship
Sauermann and Stephan w16113 Twins or Strangers? Differences and Similarities between Industrial and Academic Science
Conley and Rauscher w15873 The Effect of Daughters on Partisanship
NBER Videos

National Bureau of Economic Research, 1050 Massachusetts Ave., Cambridge, MA 02138; 617-868-3900; email:

Contact Us