NCJ Number
84565
Date Published
Unknown
Length
8 pages
Annotation
This paper explains the use of studies of twins and adopted persons in investigations of genetic and biological factors in antisocial behavior and summarizes some of the classical and recent twin and adoption studies related to behavioral genetics.
Abstract
Accurate diagnosis is essential to determine whether twins are identical (monozygotic or MZ) or fraternal (dizygotic or DZ). Comparisons of the members of MZ and DZ twin pairs can be used to determine whether genes are important in the origin of a trait. The twin method is also one of the best ways to gather information about the roles of environmental effects and is the only way to look at environmental differences while holding genotypes constant. Adoption studies try to separate the effects of genes and environment by studying children reared in an environment free of the influences of parents who provided the child's genes. However, children are not placed randomly for adoption, and the effects on research results of selective placements for such factors as ethnic background and social status are unknown. The 1941 study by Rosanoff and others of juvenile delinquency and adult crime in twins provided strong hints that delinquency as a trait behaves more like measles or some other infectious diseases than like genetically conditioned traits. However, Christiansen's definitive study of Danish twins supported the claim that genetic factors are involved in some way in the liability toward antisocial behavior. Hutchings and Mednick studied Danish adoptees and found associations between the presence or absence of offenses among the adoptees and both their biological and adoptive fathers. Both genetic and environmental effects were thus indicated. One table and seven references are provided.