Which studies compare criminal behavior in biological and non-biological relatives to separate genetics from environment?

• A. Twin Studies
• B. XYY Studies
• C. Individualistic Theories
• D. Adoption Studies

Answer: (D)

This item focuses on separating genetic influences from environmental ones by using adoption as a research design. Adoption studies compare adoptees’ criminal behavior with both their biological relatives (who share genes but not upbringing) and their adoptive relatives (who share upbringing but not genes). If criminal behavior tracks with biological relatives, genetics are suggested to play a role; if it tracks with adoptive relatives, the environment is influential. Twin studies also explore nature versus nurture but rely on identical versus fraternal twins and often involve rearing simultaneously or apart, rather than directly contrasting biological and non-biological relatives in the same way. XYY studies look at a specific genetic condition, not a design to separate genetics from environment across different kinds of relatives. Individualistic Theories are theoretical explanations rather than comparative studies of relatives. Hence, adoption studies best fit the described approach.