🧬 Twin and Adoption Studies

Question 1

Twin studies

Answer 1

If crime is genetic - identical (Mz) twins should have identical criminality

Question 2

Twin studies - findings

Answer 2

Christiansen: Concordance in
criminality Mz = 52% vs Dz = 22%

Question 3

Adoption studies

Answer 3

Adoptees share environment of adoptive parents/genes of biological parents. If genetic, criminality will match biological parents more.

Question 4

Adoption studies - findings

Answer 4

Mednick et al: birth parent
concordance = 20% vs. adopted
parent concordance = 14.7%

Question 5

Twin studies and Adoption studies - strengths

Answer 5

• Twin & adoption studies give some support to genetic explanations
• Adoption studies overcome the problem of isolating genes and environment
• Research design of Adoption studies is logical (nature vs nurture)

Question 6

Twin studies and Adoption studies - limitations

Answer 6

• If criminality was only genetic MZ twins would have 100% concordance.
• It is impossible to isolate genetic effects fully from environmental ones.
• Adopted children often placed with similar families to their birth family