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One strategy that researchers have used involves studying children of parents who were not reared by their natural parents but were adopted and reared by normal parents.
Name a research that involved this technique and what were its findings?
Mednick et al. When both adoptive and biological parents were non-criminal, 13.5% of the adoptees had a criminal record. This increased to 14.7% when adoptive parents only were criminal (environmental but not genetic predispositions present). When biological parents only were criminal the conviction rate in the adoptees increased to 20%. However, when both adoptive and biological parents were criminal the conviction rate increased to 24.5%.