Genetic explanation

• What general observation is made about offending behavior?


  Offending behavior runs in families.
• What does the genetic explanation of offending behavior suggest?


  It suggests that would-be offenders inherit genes that predispose them to crime.
• What types of studies are used to investigate genetic transmission of criminal behavior?

  Twin studies, adoption studies, and family studies.
• How many pairs of identical twins did Lange (1930) investigate?


  13 pairs of identical twins.
• What was the finding of Lange (1930) regarding MZ and DZ twins?


  30% of MZ twins had a co-twin in prison, compared to 6% of DZ twins.
• What conclusion did Lange (1930) draw from his study?


  Genetic factors must play a predominant part in offending behavior.
• What did Crowe (1972) find regarding adopted children and criminal records?


  Adopted children with a biological parent with a criminal record had a 50% risk of having a criminal record by age 18.
• What was the risk of criminal records for adopted children without a biological parent with a criminal record according to Crowe (1972)?


  5% risk of having a criminal record by age 18.
• How many males did Farrington (1996) study?


  411 males.
• What was the main finding of Farrington (1996) regarding convicted parents and their children?


  About 75% of convicted fathers and mothers had a convicted child.
• What abnormalities did Tiihonen et al. (2014) find in genes associated with violent crime?


  Abnormalities in the MAOA gene and CHD13 gene.
• What is the significance of the high-risk combination found by Tiihonen et al. (2014)?


  Individuals with this combination were 13 times more likely to have a history of violent behavior.
• What is a limitation of the studies mentioned regarding genetic factors in offending behavior?


  They cannot rule out the effect of the environment.
• How might MZ twins be treated differently than DZ twins according to the evaluation?


  MZ twins are treated similarly due to their identical appearance, increasing environmental effects.
• What does the diathesis-stress model suggest about criminal behavior?


  Genetics may predispose individuals to crime, moderated by environmental factors.
• What was the conviction rate for Danish adoptees when neither biological nor adoptive parents had a criminal conviction according to Mednick (1984)?


  13.5% conviction rate.
• How did the conviction rates change when either biological or adoptive parents had a conviction in Mednick's study?


  The rate increased to 20%.
• What was the conviction rate when both biological and adoptive parents had convictions in Mednick's study?


  24.5% conviction rate.
• What did Brunner (1993) analyze in his case study?


  The X chromosomes of 28 members of a Dutch family with a history of violence.
• What did Brunner find regarding the MAOA levels in violent men of the family?


  They had abnormally low levels of MAOA in their brains.
• What caution should be taken when generalizing findings from Brunner's case study?


  All men shared the same aggressive environment.
• What dilemma does the notion of a criminal gene present for the legal system?


  It challenges the assumption of personal and moral responsibility for actions.
• What are the key findings from Lange (1930) regarding twin studies and offending behavior?

  • 30% of MZ twins had a co-twin in prison.
  • 6% of DZ twins had a co-twin in prison.
• What are the findings from Crowe (1972) regarding adopted children and criminal records?


  • 50% risk of criminal record if biological parent has a record.
  • 5% risk if biological parent does not have a record.
• What are the findings from Farrington (1996) regarding family convictions?


  • 75% of convicted parents had a convicted child.
  • Study monitored 411 males from nearly 400 families.
• What are the findings from Tiihonen et al. (2014) regarding gene abnormalities and violent crime?

  • Abnormalities in MAOA and CHD13 genes linked to violent crime.
  • Individuals with high-risk combinations were 13 times more likely to exhibit violent behavior.
• What does the diathesis-stress model suggest about the interaction of genetics and environment in criminal behavior?


  • Genetics may predispose individuals to crime.
  • Environmental factors can moderate this predisposition.
• What are the findings from Mednick (1984) regarding convictions in Danish adoptees?


  • 13.5% conviction rate when neither parent had a conviction.
  • 20% conviction rate when either parent had a conviction.
  • 24.5% conviction rate when both parents had convictions.
• What did Brunner (1993) find in his analysis of the X chromosomes of a violent family?


  • Defect on the X chromosome present in all violent men.
  • Violent men had abnormally low levels of MAOA in their brains.
• What is the dilemma presented by the notion of a criminal gene for the legal system?


  • Challenges the assumption of personal and moral responsibility.
  • Raises questions about free will in criminal actions.