Genetics influence criminal behavior, passed from biological parent to child
Twin Studies
Types of Twins
Identical Twins (Monozygotic)
100% genetic similarity
Genetic factors attributed if both commit crimes
Non-identical Twins (Dizygotic)
Less genetic similarity
Different behaviors suggest genetic influence
Studies & Findings
Lang's Study
Higher concordance in identical twins (10 out of 13)
Lower in non-identical twins (2 out of 17)
Christansen's Study (Denmark)
35% identical twins had criminal records
Only 13.3% of non-identical twins
Ishikawa and Rain's Research
Supports genetic explanations for crime
Limitations of Twin Studies
Difficult to separate Nature vs. Nurture
Environmental influences: raised in same household
Social perceptions and differing socialization of twins
Concordance rates are not 100%
Adoption Studies
Findings
Kings and Mednik
Higher concordance between criminal biological parents and adopted children
Mednik’s Separate Study
20% risk with biological criminal parents
14.7% risk with adoptive criminal parents
Strengths and Limitations
Strengths
Reduction of social influences, focus on genetics
Limitations
Similar adoptive environments could mimic biological environments
Psychological impacts of adoption could influence behavior
Conclusion
Twin and adoption studies offer insights but have limitations in completely isolating genetic factors from environmental influences in explaining criminal behavior.