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. Author manuscript; available in PMC: 2005 Sep 23.
Published in final edited form as: Dev Psychol. 2004 May;40(3):335–351. doi: 10.1037/0012-1649.40.3.335

Figure 1.

Figure 1

Univariate quantitative genetic model. Genetic influences are represented by A, shared or “common” environmental influences by C, and nonshared environmental influences by E. The correlation between A for the twin/sibling pairs varies based on the degree of genetic relatedness. Because C represents nongenetic influences that make twins and siblings similar to one another, this path is set to 1.0. Nonshared environmental influences (E) are uncorrelated and contain measurement error. MZ = monozygotic; DZ = dizygotic; FI = full siblings in intact families; FS = full siblings in stepfamilies; HS = half siblings in stepfamilies; US = unrelated siblings in stepfamilies.