ABSTRACT
This chapter examines the empirical evidence regarding the association between intelligence, criminal behavior, and criminal justice system processing. The societal experiment of adoption is an effective and powerful method to estimate proportional influence. Adoption studies are especially valuable in discerning the shared environmental component of phenotypic variation. When describing behavioral genetics methods, intelligence is often listed along with other phenotypes, such as height, as examples of highly heritable traits. Indeed, for as long as there have been systematic assessments of human intelligence, there have been illustrations of its heritability. A relatively rare, but exceptionally powerful, version of the adoption study methodology is the monozygotic (MZ) twin reared apart method. In this hybrid natural–social experiment, researchers collect information from two individuals within an MZ twin pair who were adopted away to different homes. A common finding in the literature on intelligence is the observation of relative stability across the life course.
