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Twin Studies

  1. Soo Hyun Rhee

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy1015

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

Rhee, S. H. 2010. Twin Studies. Corsini Encyclopedia of Psychology. 1–2.

Author Information

  1. University of Colorado–Boulder

Publication History

  1. Published Online: 30 JAN 2010

Abstract

Twin studies examine the etiology of a trait by taking advantage of the fact that monozygotic (MZ) twin pairs share 100% of their genes, whereas dizygotic (DZ) twin pairs share 50% of their genes on average. By using this information and comparing the correlations of the trait in MZ and DZ twin pairs, the magnitude of three types of influences on the trait are estimated. Heritability (h2), or the magnitude of additive genetic influences, is the amount of individual differences (i.e., variance) in the liability for the trait that is due to genetic differences among individuals; c2is the magnitude of shared environmental influences, or the amount of variance in the liability for the trait that is due to environmental influences that family members experience in common and make them similar to one another; and e2is the magnitude of nonshared environmental influences, or the amount of variance in the liability for the trait that is due to environmental influences that family members experience uniquely and what makes them different from one another. It is the remainder of variance not attributed to the other factors and includes measurement error.

Keywords:

  • genetics;
  • heredity;
  • research methods;
  • nature-nurture controversy;
  • twin studies